diff --git a/Parsedown.php b/Parsedown.php
index 9059f51..918c7e6 100755
--- a/Parsedown.php
+++ b/Parsedown.php
@@ -605,19 +605,13 @@ class Parsedown
 				$index ++;
 			}
 		}
-		
-		if (strpos($text, '*') !== FALSE)
+
+		if (strpos($text, '*') !== FALSE or strpos($text, '_') !== FALSE)
 		{
-			$text = preg_replace('/\*{2}(.*?)\*{2}/', '<strong>$1</strong>', $text);
-			$text = preg_replace('/\*(.*?)\*/', '<em>$1</em>', $text);
+			$text = preg_replace('/(\*\*|__)(.+?[*_]*)(?<=\S)\1/', '<strong>$2</strong>', $text);
+			$text = preg_replace('/(\*|_)(.+?)(?<=\S)\1/', '<em>$2</em>', $text);
 		}
-		
-		if (strpos($text, '_') !== FALSE)
-		{
-			$text = preg_replace('/_{2}(\S.*?\S)_{2}/', '<strong>$1</strong>', $text);
-			$text = preg_replace('/_(\S.*?\S)_/', '<em>$1</em>', $text);
-		}
-		
+
 		$text = strtr($text, $map);
 		
 		return $text;
diff --git a/tests/data/emphasis.html b/tests/data/emphasis.html
index 2adbd1a..bcb613b 100644
--- a/tests/data/emphasis.html
+++ b/tests/data/emphasis.html
@@ -1,5 +1,8 @@
 <p>Here's <em>an emphasis</em>.</p>
+<p>A short emphasis <em>a</em> <em>b</em> .</p>
 <p>Here's <strong>a strong one</strong>. </p>
 <p>Here's <em>an emphasis that uses underscores</em>. </p>
 <p>Here's <strong>a strong emphasis that uses underscores</strong>.</p>
-<p>This is _ not an emphasis _.</p>
\ No newline at end of file
+<p>This is _ not an emphasis _ neither is * that * .</p>
+<p>Empty emphasis ** is not __ an emphasis.</p>
+<p>Three asterisks are an emphasized asterisk <em>*</em> .</p>
\ No newline at end of file
diff --git a/tests/data/emphasis.md b/tests/data/emphasis.md
index 45b57c0..1adc218 100644
--- a/tests/data/emphasis.md
+++ b/tests/data/emphasis.md
@@ -1,9 +1,15 @@
 Here's *an emphasis*.
 
+A short emphasis _a_ *b* .
+
 Here's **a strong one**. 
 
 Here's _an emphasis that uses underscores_. 
 
 Here's __a strong emphasis that uses underscores__.
 
-This is _ not an emphasis _.
\ No newline at end of file
+This is _ not an emphasis _ neither is * that * .
+
+Empty emphasis ** is not __ an emphasis.
+
+Three asterisks are an emphasized asterisk *** .
\ No newline at end of file