The role of genes implicated in the regulation of spermatogenesis and their patterns of expression is still poorly understood. In this study, we took advantage of the cystic arrangement of the teleost testis to set up a laser capture microdissection procedure to isolate cells from cysts containing spermatogonia, spermatocytes, spermatids, or spermatozoa. We then used quantitative PCR to determine the stage-specific expression patterns of the germ cell marker vasa; gonadal aromatase (cyp19a); estrogen receptors (ers) alpha, beta1, and beta2 (era, erb1, and erb2, respectively); 11beta-hydroxylase (cyp11b1); androgen receptor beta (arb); insulinlike growth factor 1 (igf1); and sox17. vasa had the highest mRNA levels, followed by genes involved in androgen metabolism (cyp11b1 and arb). Most genes associated with estrogen metabolism (cyp19a, era, and erb1) had a lower expression, whereas igf1 and sox17 exhibited the lowest mRNA levels. Comparison of changes in mRNA levels revealed five patterns of gene expression, in general with progressively lower expression seen as spermatogenesis advanced. igf1 and sox17 were exclusively expressed in spermatogonia-containing cysts, suggesting effects during the proliferative stage. Genes involved in androgen synthesis (cyp11b1) and action (arb) peaked during the early stages of spermatogenesis and then sharply decreased. In contrast, genes associated with estrogen action, particularly erb2 and era, showed a more gradual decrease. Together, these results demonstrate the usefulness of fish models and suggest that whereas androgens are required at high levels and may exert their major actions at the initial stages of spermatogenesis, estrogens are also essential, albeit required at lower levels, and with a more generalized influence.