The spermatogenic cycles of Podarcis bocagei and P. carbonelli, two lacertids previously considered conspecific, were analysed in northwest Portugal. Monthly sampling was carried out at three sites: a zone of strict syntopy and two sites of allopatry for both species, all of them geographically close and harbouring similar habitats. The maritime Atlantic climate, which allows males to remain active most of the year, plays a determinant role on the variation of the mixed-type cycle, typical of lacertids in temperate regions. Comparison with other populations and species indicates that climate modifies the pattern of spermatogenesis by restricting the beginning (but not the end) of the activity period. Results also corroborate previous studies that report an agreement between the variations in the gonads observed at both microscopic and macroscopic scales in the reproductive period. Peaks for spermatozoa were delayed in sympatry but competition cannot be directly concluded. Furthermore, relationships between the number of spermatozoa and body size suggest sperm competition and possibly a reproductive interaction between the species.