Let

be the Riemann integral over [0,A] of a realization of a random process

with stationary independent increments (SII), finite second moments, and

. The optimal design, consisting of n distinct observation times, for estimating

relative to a mean-squared error optimality criterion is shown to be the design such that

, independent of the parameters of the process. The mean-squared error of the optimal estimate is displayed. The optimal design for estimating the integral over a proper subinterval of [0,A] is also derived.