To find the common ratio of a geometric sequence, you can divide any term by its preceding term.
In the given sequence: -2, 4, -8, 16, -32, ...
Let's calculate the common ratio \( r \) using the first two terms:
\[ r = \frac{4}{-2} = -2 \]
Now, let's check this ratio with the next pair of terms:
\[ r = \frac{-8}{4} = -2 \]
And the next pair:
\[ r = \frac{16}{-8} = -2 \]
And one more pair:
\[ r = \frac{-32}{16} = -2 \]
In all cases, the common ratio is consistent. Therefore, the common ratio of the geometric sequence is:
\[ \boxed{-2} \]