Phytoplankton production was investigated throughout the whole Benguela ecosystem in winter 1999 and in summer 2002 during two four-week research cruises from Cape Town, South Africa, through Namibian waters to Namibe in southern Angola. Primary production ranged from 0.14–2.26 g C m⁻² d⁻¹ during June–July 1999 and from 0.39–8.83 g C m⁻² d⁻¹ during February–March 2002. Mean productivity values indicated that the Benguela ecosystem was twice as productive in summer than in winter. In 1999, most of the productivity occurred within a temperature range of 13.5–18 °C, whereas in 2002 elevated production was associated with temperatures of 14–22 °C. The relationship between primary production and chlorophyll a was good for winter 1999 but poor for summer 2002, suggesting that predicting primary production from chlorophyll a is not straightforward for the Benguela ecosystem. Keywords: chlorophyll a, primary production, temperature.