The higher Lepidoptera produce two types of sperm, eupyrene and apyrene. Eupyrene spermatozoa are fertile, while apyrene spermatozoa are anucleate and, therefore, sterile. Meiosis differs between the two developmental lines. One of the most obvious differences is the aberrant organization of the apyrene spindles. They possess fewer microtubules than eupyrene spindles and chromosome segregation is irregular. To determine whether micotubule nucleation is impaired in the aprene spindles, the present fine structure study concentrated on the centrosomes in both spermatocyte types. In addition, the presence of gamma-tubulin, a newly discovered tubulin isoform which is prevalent in centrosomes, was determined by anti-tubulin immunofluorescence. The observations showed that centrosome fine structure and appearance of gamma-tubulin containing polar masses were very similar in eupyrene and apyrene spermatocytes in late prophase I and in more advanced cells with spindle formation completed. In particular, pericentriolar material was present in about equal quantities in both cell types. Thus, the aberrant structure and behaviour of apyrene spindles are probably not caused by deficiencies in the amount of pericentriolar material and gamma-tubulin, a molecule which is crucial for microtubule nucleation.