AbstractThe Baltic Sea has been subject to an increased load of nutrients during the last century. The effect of this load is obscured sometimes by a lack of data but always by large seasonal variations. A non‐parametric method was used for trend tests at nine different sampling stations from the whole Baltic Sea. Time series from 1968–1990, based on data from HELCOM and ICES databases, were analyzed for trend in concentrations of NO3, NH4, PO4, total phosphorous and total nitrogen.About 60% of the test statistics gave significant trends at 5% confidence levels. Total nitrogen, total phosphorous, NO3, and PO4have generally increased in the Baltic Sea. The increase is in the range of 1–4% yr−1. Ammonium shows decreasing trend in the Baltic Sea, with a slope of 3–8% yr−1. Regional differences are, however, found for most of the c