Abstract: In this paper, we investigate -average sampling numbers of a periodic Sobolev space with a Gaussian measure in the metric for and , and obtain their asymptotic orders. Moreover, we show that in the average case setting, the operators , which are the Lagrange interpolating operators, are asymptotically optimal in the metric for all . It is interesting to note that in the worst case setting, are not asymptotically optimal algorithms in the metric for or . [Copyright &y& Elsevier]