Diel and seasonal variations in abundance, population structure, biomass and production rate of the planktonic calanoid copepod Temora turbinata were studied in the Cananéia Lagoon estuarine system, São Paulo, Brazil. Zooplankton sample collections were carried out at 4-h intervals over multiple 24-h periods, from February 1995 to January 1996. Temora turbinata was present in the plankton all year round (temperature, 18.6-29.6°C; salinity, 8-33 psu; chlorophyll a concentration, 1.32-15.33 µg l^-1). Temora turbinata showed considerable diel variations in abundance. Abundance of T. turbinata was higher from June to October when temperature was lower than ca. 24°C and salinity was higher than ca. 20 psu. The biomass varied from 0.0005 ± 0.0014 to 3.715 ± 2.360 mgC m^-3 (daily mean ± SD). The daily production rates estimated by the Hirtst-Sheader models varied from 0.0002 ± 0.0006 to 1.115 ± 0.261 mgC m^-3 d^-1 (mean ± SD). The P/B ratios varied from 0.17 to 0.45 d^-1. These results showed that T. turbinata constituted 8.3 and 7.8% of the annual copepod community biomass and production rate respectively.