Here is what happens when there are more than 4 input variables.  Basically,
you get to play 3-dimensional chess ... the first Kmap essentially sits on top
of the second.  For example, in the figure below, the 16 squares of the first 
map are where A is high, and the second 16 squares are where A is low.

Suppose we have the equation 

A*!B*!E + !A*!B*!D*E + A*B*D*E + !A*!B*C*!D + A*!B*C*E + !A*B*D*E
   T1          T2          T3         T4          T5         T6

(I have numbered each term T1-T6, so you can see on the maps where they go.)

Here is the filled-out Kmap.

A                  |      B             
     +-------------+-------------+
     |  T1  | T1   |      |      | 
     |------+------+------+------+---
     |      | T5   |      |      |
  ---+------+------+------+------| E
     |      | T5   |  T3  |  T3  |
   D |------+------+------+------+---
     | T1   | T1   |      |      |
     +------+-------------+------+
            |      C      |


!A                 |      B            
     +-------------+-------------+
     |      |  T4  |      |      | 
     |------+------+------+------+---
     |  T2  | T2,T4|      |      |
  ---+------+------+------+------| E
     |      |      |  T6  |  T6  |
   D |------+------+------+------+---
     |      |      |      |      |
     +------+-------------+------+
            |      C      |

Remember, since the A plane sits on top of the !A plane, we have to remember to
look for Prime Implicants that cross planes as well as lie within a plane.  So,
for example, there is a Prime Implicant that includes both T3 and T6, giving
the term B*D*E ... 

The total set of prime implicants in this diagram are 
A*!B*!E + A*!B*C + !A*!B*!D*E + !B*C*!D + B*D*E

The first term (A*!B*!E) is the four T1's in the A plane
The second term (A*!B*C) is the vertical group in the A plane consisting of the 
	two T5's and the two T1's next to them
The third term (!A*!B*!D*!E) is the two T2's in the !A plane
The fourth term (!B*C*!D) is the the two T4's in the !A plane and the T1 and T5
	directly above them (in the A plane)
The fifth term (B*D*E) is the two T6's in the !A plane and the two T3's 
	directly above them in the A plane