<p>If I am evaluating two variables and not two method calls does it matter weather I use "&amp;&amp;" or "&amp;"</p>

<pre><code>//some logic that sets bool values

boolean X = true;
boolean Y = true;

if (X &amp; Y){
   // perform some operation
}

if (X &amp;&amp; Y){
   // perform some operation
}
</code></pre>

<p>Further a book I am using for C# 3.0 / .NET 3.5 only makes reference to the &amp;&amp; operator, is the &amp; operator going away?</p>

Always use && if you are performing a true/false logic test. A single & performs a bit-wise 'and'.  It make work like a logic test in some cases but it is not guaranteed to work for all logic cases.  The most common use of a single & is when applying a bit-mask.
Examples (&&):
```
```
true && true == true
```
```
Example (&):
```
```
00101001 & 00100001 = 00100001
```
```