1diff --git a/README.md b/README.md
  2index b6c62ad..929b694 100644
  3--- a/README.md
  4+++ b/README.md
  5@@ -26,4 +26,6 @@ The resulting errors from these bugs aren't that bad. I'll mark them down, and i
  6 How do we protect against users injecting data that looks like `console.log(sensitive_data)` when we evaluate variables
  7 inside parser.js? If we ever want to impliment custom formulas, or even accept data in raw format, we need to guard
  8 against this. Or else someone could load a CSV with javascript and when our spreadsheet opens it, then suddenly
  9-arbitrary javascript is executed in the client machine.
 10\ No newline at end of file
 11+arbitrary javascript is executed in the client machine.
 12+
 13+### Criteria evaluations should accept "<>"
 14\ No newline at end of file
 15diff --git a/src/RawFormulas/RawFormulas.ts b/src/RawFormulas/RawFormulas.ts
 16index ab64252..12d9734 100644
 17--- a/src/RawFormulas/RawFormulas.ts
 18+++ b/src/RawFormulas/RawFormulas.ts
 19@@ -70,7 +70,6 @@ import { CellError } from "../Errors"
 20 import * as ERRORS from "../Errors"
 21 
 22 var ACCRINT = Formula["ACCRINT"];
 23-var AVERAGEIF = Formula["AVERAGEIF"];
 24 var BIN2DEC = Formula["BIN2DEC"];
 25 var BIN2HEX = Formula["BIN2HEX"];
 26 var BIN2OCT = Formula["BIN2OCT"];
 27@@ -129,6 +128,37 @@ var SUMX2PY2 = Formula["SUMX2PY2"];
 28 var TRUNC = Formula["TRUNC"];
 29 var YEARFRAC = Formula["YEARFRAC"];
 30 
 31+/**
 32+ * Returns the average of a range depending on criteria.
 33+ * @param values[0] criteria_range - The range to check against criterion.
 34+ * @param values[1] criterion - The pattern or test to apply to criteria_range.
 35+ * @param values[2] average_range - [optional] The range to average. If not included, criteria_range is used for the
 36+ * average instead.
 37+ * @returns {number}
 38+ * @constructor
 39+ * TODO: This needs to take nested range values.
 40+ * TODO: This needs to also accept a third parameter "average_range"
 41+ */
 42+var AVERAGEIF = function (...values) {
 43+  checkArgumentsLength(values, 2);
 44+  var range = values[0];
 45+  var criteriaEvaluation = CriteriaFunctionFactory.createCriteriaFunction(values[1]);
 46+
 47+  var result = 0;
 48+  var count = 0;
 49+  for (var i = 0; i < range.length; i++) {
 50+    var val = valueToNumber(range[i]);
 51+    if (criteriaEvaluation(val)) {
 52+      result = result + val;
 53+      count++;
 54+    }
 55+  }
 56+  if (count === 0) {
 57+    throw new CellError(ERRORS.DIV_ZERO_ERROR, "Evaluation of function AVERAGEIF caused a divide by zero error.");
 58+  }
 59+  return result / count;
 60+};
 61+
 62 /**
 63  * Rounds a number up to the nearest integer multiple of specified significance.
 64  * @param values[0] The value to round up to the nearest integer multiple of factor.
 65@@ -230,6 +260,7 @@ var COUNT = function (...values) : number {
 66  * front of them. If it is neither, it will compared with values in the range using equality comparison.
 67  * @returns {number}
 68  * @constructor
 69+ * TODO: This needs to take nested range values.
 70  */
 71 var COUNTIF = function (...values) {
 72   checkArgumentsLength(values, 2);
 73@@ -248,6 +279,15 @@ var COUNTIF = function (...values) {
 74   return count;
 75 };
 76 
 77+/**
 78+ * Returns the count of a range depending on multiple criteria.
 79+ * @param values[0] criteria_range1 - The range to check against criterion1.
 80+ * @param values[1] criterion1 - The pattern or test to apply to criteria_range1.
 81+ * @param values[2...N] Repeated sets of ranges and criterion to check.
 82+ * @returns {number} count
 83+ * @constructor
 84+ * TODO: This needs to take nested range values.
 85+ */
 86 var COUNTIFS = function (...values) {
 87   checkArgumentsAtLeastLength(values, 2);
 88   var criteriaEvaluationFunctions = values.map(function (criteria, index) {
 89@@ -380,6 +420,7 @@ var ROUNDUP = function (...values) {
 90  * @param values[2] (optional) The range to be summed, if different from range.
 91  * @returns {number}
 92  * @constructor
 93+ * TODO: This needs to take nested range values.
 94  */
 95 var SUMIF = function (...values) {
 96   checkArgumentsAtWithin(values, 2, 3);
 97diff --git a/tests/FormulasTest.ts b/tests/FormulasTest.ts
 98index aec77ae..c746642 100644
 99--- a/tests/FormulasTest.ts
100+++ b/tests/FormulasTest.ts
101@@ -258,7 +258,33 @@ catchAndAssertEquals(function() {
102 }, ERRORS.REF_ERROR);
103 
104 
105+// Test AVERAGEIF
106 assertEquals(AVERAGEIF([1, 5, 10], '>2'), 7.5);
107+assertEquals(AVERAGEIF([1, 5, 10], ">4"), 7.5);
108+assertEquals(AVERAGEIF([1, 2, 2, 2, 2, 2, 2, 2], ">1"), 2);
109+assertEquals(AVERAGEIF([1, 5, 10], 5), 5);
110+assertEquals(AVERAGEIF([1, 5, 5, 5, 10, 5], 5), 5);
111+assertEquals(AVERAGEIF([1, 5, 5, 5, 10, 5], 10), 10);
112+assertEquals(AVERAGEIF([1, 5, 5, 5, 10, 5], ">5"), 10);
113+assertEquals(AVERAGEIF([1, 5, 5, 5, 10, 5], "=5"), 5);
114+assertEquals(AVERAGEIF([1, 5, 5, 5, 10, 5], "=10"), 10);
115+assertEquals(AVERAGEIF([1, 5, 5, 5, 10, 5], "=     10  "), 10);
116+assertEquals(AVERAGEIF([1, 5, 5, 5, 10, 5], ">0"), 5.166666666666667);
117+assertEquals(AVERAGEIF([1, 5, 5, 5, 10, 5], ">=5"), 6);
118+assertEquals(AVERAGEIF([1, 5, 5, 5, 10, 5], "<10"), 4.2);
119+assertEquals(AVERAGEIF([1, 5, 5, 5, 10, 5, 44], "<=10"), 5.166666666666667);
120+assertEquals(AVERAGEIF([1, 5, 5, 5, 10, 5], ">4.99"), 6);
121+assertEquals(AVERAGEIF([1, 5, 5, 5, 10, 5], "<4.99"), 1);
122+catchAndAssertEquals(function() {
123+  AVERAGEIF([1, 5, 5, 5, 10, 5], "=     1.0.0  ");
124+}, ERRORS.DIV_ZERO_ERROR);
125+catchAndAssertEquals(function() {
126+  AVERAGEIF([1, 5, 5, 5, 10, 5], "=>5");
127+}, ERRORS.DIV_ZERO_ERROR);
128+catchAndAssertEquals(function() {
129+  AVERAGEIF([1, 5, 5, 5, 10, 5], "==5");
130+}, ERRORS.DIV_ZERO_ERROR);
131+
132 
133 assertEquals(BIN2DEC(1010101010), -342);
134