Data on mercury levels in freshwater fish (mainly pike, perch, trout and char), from Norway, Sweden and Finland have been collected in a common database to assess spatial patterns as well as relationships with environmental factors such as atmospheric mercury deposition. A preliminary evaluation of fish Hg data from >1500 lakes shows that Hg levels referring to a 1-kg pike are highest in low-altitude lakes of the southern regions S. Norway, S+C. Sweden, and C. Finland, where regional medians are 0.5-0.8 mg/kg fw. In these regions, about 50-80 % of the lakes exceed 0.5 mg/kg and about 5-20(40) % of the lakes exceed 1.0 mg/kg. Fish Hg levels in high-altitude lakes are lower than in low-altitude lakes in the corresponding region.