diff --git a/UPGRADE b/UPGRADE
index b97f377a..cdbbda80 100644
--- a/UPGRADE
+++ b/UPGRADE
@@ -129,6 +129,8 @@ OTHER CHANGES:
 25. Added new LOCK options to Manual Dial Search Checkbox to prevent the agent
 	from checking or unchecking the search checkbox.
 
+26. Added case-sensitive user ID validation on agent login.
+
 
 
 
diff --git a/www/agc/timeclock.php b/www/agc/timeclock.php
index 7d87bd9a..8203254c 100644
--- a/www/agc/timeclock.php
+++ b/www/agc/timeclock.php
@@ -19,10 +19,11 @@
 # 141118-1239 - Formatting changes for QXZ output
 # 141216-2122 - Added language settings lookups and user/pass variable standardization
 # 150210-1307 - Fixed QXZ tags and formatting(issue #827)
+# 150212-0033 - Added case-sensitive user validation(issue #682)
 #
 
-$version = '2.10-14';
-$build = '141216-2122';
+$version = '2.10-15';
+$build = '150212-0033';
 
 $StarTtimE = date("U");
 $NOW_TIME = date("Y-m-d H:i:s");
@@ -99,7 +100,7 @@ require_once("functions.php");
 #############################################
 ##### START SYSTEM_SETTINGS AND USER LANGUAGE LOOKUP #####
 $VUselected_language = '';
-$stmt="SELECT selected_language from vicidial_users where user='$VD_login';";
+$stmt="SELECT user,selected_language from vicidial_users where user='$VD_login';";
 if ($DB) {echo "|$stmt|\n";}
 $rslt=mysql_to_mysqli($stmt, $link);
 	if ($mel > 0) {mysql_error_logging($NOW_TIME,$link,$mel,$stmt,'00XXX',$VD_login,$server_ip,$session_name,$one_mysql_log);}
@@ -107,7 +108,8 @@ $sl_ct = mysqli_num_rows($rslt);
 if ($sl_ct > 0)
 	{
 	$row=mysqli_fetch_row($rslt);
-	$VUselected_language =		$row[0];
+	$VUuser =				$row[0];
+	$VUselected_language =	$row[1];
 	}
 
 $stmt = "SELECT use_non_latin,admin_home_url,admin_web_directory,enable_languages,language_method FROM system_settings;";
@@ -147,6 +149,15 @@ if ( ($stage == 'login') or ($stage == 'logout') )
 	if ($auth_message == 'GOOD')
 		{$valid_user=1;}
 
+	# case-sensitive check for user
+	if($valid_user>0)
+		{
+		if ($user != "$VUuser") 
+			{
+			$valid_user=0;
+			}
+		}
+
 	print "<!-- vicidial_users active count for $user:   |$valid_user| -->\n";
 
 	if ($valid_user < 1)
diff --git a/www/agc/vicidial.php b/www/agc/vicidial.php
index eb3d476c..2e9794b8 100644
--- a/www/agc/vicidial.php
+++ b/www/agc/vicidial.php
@@ -477,10 +477,11 @@
 # 150203-1331 - Small changes to improve manual dial hotkey use
 # 150204-1911 - Changed Manual hotkey auto-manual-dial to a variable delay depending on dispo processing time
 # 150210-1225 - Added LOCK options for manual_dial_search_checkbox, fixed missing QXZ tags(issue #827)
+# 150212-0034 - Added case-sensitive user validation(issue #682)
 #
 
-$version = '2.10-448c';
-$build = '150210-1225';
+$version = '2.10-449c';
+$build = '150212-0034';
 $mel=1;					# Mysql Error Log enabled = 1
 $mysql_log_count=85;
 $one_mysql_log=0;
@@ -563,7 +564,7 @@ $VUselected_language = '';
 $random = (rand(1000000, 9999999) + 10000000);
 
 
-$stmt="SELECT selected_language from vicidial_users where user='$VD_login';";
+$stmt="SELECT user,selected_language from vicidial_users where user='$VD_login';";
 if ($DB) {echo "|$stmt|\n";}
 $rslt=mysql_to_mysqli($stmt, $link);
 	if ($mel > 0) {mysql_error_logging($NOW_TIME,$link,$mel,$stmt,'01081',$VD_login,$server_ip,$session_name,$one_mysql_log);}
@@ -571,7 +572,8 @@ $sl_ct = mysqli_num_rows($rslt);
 if ($sl_ct > 0)
 	{
 	$row=mysqli_fetch_row($rslt);
-	$VUselected_language =		$row[0];
+	$VUuser =				$row[0];
+	$VUselected_language =	$row[1];
 	}
 
 #############################################
@@ -1122,6 +1124,15 @@ else
 			$auth=1;
 			$pass_hash = preg_replace("/GOOD\|/",'',$auth_message);
 			}
+		# case-sensitive check for user
+		if($auth>0)
+			{
+			if ($VD_login != "$VUuser") 
+				{
+				$auth=0;
+				$auth_message='ERRCASE';
+				}
+			}
 
 		if($auth>0)
 			{
@@ -2202,6 +2213,8 @@ else
 				{$VDdisplayMESSAGE = _QXZ("You are already logged in, please log out of your other session first")."<br />";}
 			if ($auth_message == 'ERRAGENTS')
 				{$VDdisplayMESSAGE = _QXZ("Too many agents logged in, please contact your administrator")."<br />";}
+			if ($auth_message == 'ERRCASE')
+				{$VDdisplayMESSAGE = _QXZ("Login incorrect, user names are case sensitive")."<br />";}
 			}
 		}
 	if ($VDloginDISPLAY)