  We prove that self-avoiding walk on Z^d is sub-ballistic in any dimension d
at least two. That is, writing ||u|| for the Euclidean norm of u \in Z^d, and
SAW_n for the uniform measure on self-avoiding walks gamma:{0,...,n} \to Z^d
for which gamma_0 = 0, we show that, for each v > 0, there exists c > 0 such
that, for each positive integer n, SAW_n (max {|| gamma_k || : k \in {0,...,n}}
> v n) < e^{- c n}.
