Filtration rate values with neutral red were analyzed in 60 mangrove oysters, Crassostrea rhizophorae, in two experiments; one with salinities of 10, 20, 25, 30 and 35 o/oo at a constant 24°C temperature and the other with temperatures of 24, 28, 32 and 34°C at a cunstant 25 o/oo salinity. The optimal filtration rate occurred at a 25 o/oo salinity and a 28°C temperature.