The spiny and slipper lobster fisheries are amongst the most important economical activities for the Galapagos Islands, currently with management schemes involving a season, a minimum landing size, No-Take Zones, and protection of berried females for the red spiny lobster, Panulirus penicillatus, whilst the Galapagos slipper lobster, Scyllarides astori, only has NTZs and protection of berried females. By means of nocturnal SCUBA diving surveys carried out from December 2000 to January 2004, a total of 1075 female slipper lobsters and 1142 female red spiny lobsters was collected in horizontal surveys along a stretch of coastline. Total length (TL), carapace length (CL), and presence of eggs was recorded for both species. Size at 50% maturity was recorded as 22.6 cm TL for red spiny lobster and 22.1 cm TL for the slipper lobster. The smallest individuals with mature eggs were 15.2 cm TL and 20.1 cm TL for red spiny lobster and slipper lobster, respectively. Fecundity values presented high variation with size, with values ranging between 200 000 and 600 000 for the red spiny lobster and 87 000-360 000 for the slipper lobster. For red spiny lobster, we recorded the presence of 23.3% ovigerous females above the minimum size at maturity throughout the study, with higher values in November 2001 and January 2004; whilst for the slipper lobster a total of 14.8% of the females above the minimum size at maturity was ovigerous, with higher values during warmer months. For both species, data suggest increased reproductive activity with higher SST values. With the revision of the Five-Year Fishing Calendar, this information should be incorporated so as to aid stakeholders and management authorities of the Galapagos Marine Reserve assess the conservation status of both species, and ensure a thorough management plan aimed at the sustainable use of these resources.