Let M(X) be the collection of
probability measures on the Borel sets of a Polish space X. The Borel structure of
M(X) generated by the weak∗ topology is investigated. Various collections of
probability measures arising in nonparametric statistics are shown to Borel sets of
M(X). Attention is particularly focused on collections arising from restrictions on
distribution functions, density functions, and supports of the underlying probability
measures.