Nucleolar development and nucleolar organizer (NOR) activity are analyzed during spermatogenesis ofSchistocerca gregariaby silver impregnation. Two NORs located distally in M6and proximally in S9show activity during early prophase of the first meiotic division. A reactivation of the NORs with the appearance of nucleolar masses and a chromosome arrangement in which all centromeres are placed in the nuclear base are observed in spermatids. Different aspects related to the location of NORs and the N-banding patterns based in previous observations are discussed.