The primary production of phytoplankton was measured using the C-14-technique in situ from 1985 to 1996 at the mouth of the Gullmar Fjord, located on the Swedish west coast. The mean annual primary production for these 12 years was 241 gC m(-2) year(-1), with an inter-annual Variation of 180 to 339 gC m(-2) year(-1). Time series of monthly means of the North Atlantic Oscillation (NAO), wind, temperature, salinity, nutrients, precipitation, run-off, chlorophyll a, and primary production were compared using correlations on both original and detrended series. The direct correlations with primary production without any time-lag were negative with SE, NW, SW winds and with local and Kattegat run-off. With a 6-month time lag, primary production was strongly positively correlated with SE and NW winds as well as with Kattegat run-off and weakly positively correlated with SW winds. The results suggest the presence of an indirect Link between NAG, the supply of nutrients to Kattegat, wind, and the primary production in the Gullmar Fjord. (C) 1998 International Council for the Exploration of the Sea.