1diff --git a/DOCS.md b/DOCS.md
  2index b68baeb..acf8f25 100644
  3--- a/DOCS.md
  4+++ b/DOCS.md
  5@@ -454,6 +454,15 @@
  6 @returns {boolean}. 
  7 @constructor
  8 ```
  9+
 10+### ISLOGICAL 
 11+
 12+```
 13+  Returns true if value is a boolean (FALSE, or TRUE). Numerical and text values return false. 
 14+@param value - value or reference to check. 
 15+@returns {boolean} 
 16+@constructor
 17+```
 18 ## Logical
 19 
 20 
 21diff --git a/TODO.md b/TODO.md
 22index e4cc06e..3b5ddd0 100644
 23--- a/TODO.md
 24+++ b/TODO.md
 25@@ -31,7 +31,6 @@ For example 64 tbs to a qt.
 26 * ISERR
 27 * ISERROR
 28 * ISFORMULA
 29-* ISLOGICAL
 30 * ISNA
 31 * ISNONTEXT
 32 * ISNUMBER
 33diff --git a/dist/Formulas/AllFormulas.js b/dist/Formulas/AllFormulas.js
 34index c5cd84a..aecda72 100644
 35--- a/dist/Formulas/AllFormulas.js
 36+++ b/dist/Formulas/AllFormulas.js
 37@@ -74,6 +74,7 @@ exports.UMINUS = Math_1.UMINUS;
 38 var Info_1 = require("./Info");
 39 exports.NA = Info_1.NA;
 40 exports.ISTEXT = Info_1.ISTEXT;
 41+exports.ISLOGICAL = Info_1.ISLOGICAL;
 42 var Lookup_1 = require("./Lookup");
 43 exports.CHOOSE = Lookup_1.CHOOSE;
 44 var Logical_1 = require("./Logical");
 45diff --git a/dist/Formulas/Info.js b/dist/Formulas/Info.js
 46index 18152ae..7235711 100644
 47--- a/dist/Formulas/Info.js
 48+++ b/dist/Formulas/Info.js
 49@@ -2,6 +2,7 @@
 50 exports.__esModule = true;
 51 var ArgsChecker_1 = require("../Utilities/ArgsChecker");
 52 var Errors_1 = require("../Errors");
 53+var TypeConverter_1 = require("../Utilities/TypeConverter");
 54 /**
 55  * Returns the "value not available" error, "#N/A".
 56  * @constructor
 57@@ -19,6 +20,17 @@ exports.NA = NA;
 58  */
 59 var ISTEXT = function (value) {
 60     ArgsChecker_1.ArgsChecker.checkLength(arguments, 1, "ISTEXT");
 61-    return typeof value === "string";
 62+    return typeof TypeConverter_1.TypeConverter.firstValue(value) === "string";
 63 };
 64 exports.ISTEXT = ISTEXT;
 65+/**
 66+ * Returns true if value is a boolean (FALSE, or TRUE). Numerical and text values return false.
 67+ * @param value - value or reference to check.
 68+ * @returns {boolean}
 69+ * @constructor
 70+ */
 71+var ISLOGICAL = function (value) {
 72+    ArgsChecker_1.ArgsChecker.checkLength(arguments, 1, "ISLOGICAL");
 73+    return typeof TypeConverter_1.TypeConverter.firstValue(value) === "boolean";
 74+};
 75+exports.ISLOGICAL = ISLOGICAL;
 76diff --git a/src/Formulas/AllFormulas.ts b/src/Formulas/AllFormulas.ts
 77index 290d75e..b3ef233 100644
 78--- a/src/Formulas/AllFormulas.ts
 79+++ b/src/Formulas/AllFormulas.ts
 80@@ -72,7 +72,8 @@ import {
 81 } from "./Math";
 82 import {
 83   NA,
 84-  ISTEXT
 85+  ISTEXT,
 86+  ISLOGICAL
 87 } from "./Info";
 88 import {
 89   CHOOSE
 90@@ -329,5 +330,6 @@ export {
 91   STDEVA,
 92   STDEVP,
 93   STDEVPA,
 94-  ISTEXT
 95+  ISTEXT,
 96+  ISLOGICAL
 97 }
 98\ No newline at end of file
 99diff --git a/src/Formulas/Info.ts b/src/Formulas/Info.ts
100index 2f3b5b9..21c9e1c 100644
101--- a/src/Formulas/Info.ts
102+++ b/src/Formulas/Info.ts
103@@ -4,6 +4,9 @@ import {
104 import {
105   NAError
106 } from "../Errors";
107+import {
108+  TypeConverter
109+} from "../Utilities/TypeConverter";
110 
111 
112 /**
113@@ -24,11 +27,24 @@ var NA = function () {
114  */
115 var ISTEXT =  function (value) {
116   ArgsChecker.checkLength(arguments, 1, "ISTEXT");
117-  return typeof value === "string";
118+  return typeof TypeConverter.firstValue(value) === "string";
119+};
120+
121+
122+/**
123+ * Returns true if value is a boolean (FALSE, or TRUE). Numerical and text values return false.
124+ * @param value - value or reference to check.
125+ * @returns {boolean}
126+ * @constructor
127+ */
128+var ISLOGICAL = function (value) {
129+  ArgsChecker.checkLength(arguments, 1, "ISLOGICAL");
130+  return typeof TypeConverter.firstValue(value) === "boolean";
131 };
132 
133 
134 export {
135   NA,
136-  ISTEXT
137+  ISTEXT,
138+  ISLOGICAL
139 }
140\ No newline at end of file
141diff --git a/tests/Formulas/InfoTest.ts b/tests/Formulas/InfoTest.ts
142index dfa8d6c..a7d0954 100644
143--- a/tests/Formulas/InfoTest.ts
144+++ b/tests/Formulas/InfoTest.ts
145@@ -1,6 +1,7 @@
146 import {
147   NA,
148-  ISTEXT
149+  ISTEXT,
150+  ISLOGICAL
151 } from "../../src/Formulas/Info";
152 import * as ERRORS from "../../src/Errors";
153 import {
154@@ -18,9 +19,20 @@ test("NA", function(){
155 
156 test("ISTEXT", function(){
157   assertEquals(ISTEXT("str"), true);
158+  assertEquals(ISTEXT(["str"]), true);
159   assertEquals(ISTEXT(9), false);
160   assertEquals(ISTEXT(false), false);
161   catchAndAssertEquals(function() {
162     ISTEXT.apply(this, []);
163   }, ERRORS.NA_ERROR);
164 });
165+
166+test("ISLOGICAL", function(){
167+  assertEquals(ISLOGICAL("str"), false);
168+  assertEquals(ISLOGICAL(9), false);
169+  assertEquals(ISLOGICAL(false), true);
170+  assertEquals(ISLOGICAL(true), true);
171+  catchAndAssertEquals(function() {
172+    ISLOGICAL.apply(this, []);
173+  }, ERRORS.NA_ERROR);
174+});
175diff --git a/tests/SheetFormulaTest.ts b/tests/SheetFormulaTest.ts
176index c49c767..51198ca 100644
177--- a/tests/SheetFormulaTest.ts
178+++ b/tests/SheetFormulaTest.ts
179@@ -659,6 +659,10 @@ test("Sheet ISTEXT", function(){
180   assertFormulaEquals('=ISTEXT("str")', true);
181 });
182 
183+test("Sheet ISLOGICAL", function(){
184+  assertFormulaEquals('=ISLOGICAL(true)', true);
185+});
186+
187 test("Sheet *", function(){
188   assertFormulaEquals('= 10 * 10', 100);
189   assertFormulaEquals('= 10 * 0', 0);