Let theta(a) be the first time when the range (R(n); n greater than or
equal to 0) is equal to a, R(n) being equal to the difference of the
maximum and the minimum, taken at time n, of a simple random walk on Z
. We compute the g.f. of theta(a); this allows us to compute the distr
ibutions of theta(a) and R(n). We also investigate the asymptotic beha
viour of theta(n), n going to infinity.