Macrozoobenthic zonation in relation to major environmental factors across the Archipelago Sea, northern Baltic Sea. Boreal Env. Res. 8: 159–170. ISSN 1239-6095 Benthic macrofaunal assemblages from a series of samples taken between 1994 and 2000 across the Archipelago Sea are described, and community structure in relation to major environmental factors analysed. Results provided a clear division of the Archi-pelago Sea into three zones based on benthic species composition. Environmental fac-tors which best explained the observed species distribution, i.e. temperature, salinity, dissolved oxygen, and sediment organic carbon were seen to operate along a cline of increasing depth. An east–west comparison of adjacent zones was also investigated. These closely resembled one another showing few signifi cant differences. Local environmental factors were considered responsible where differences were observed. Evidence of a marked temporal difference in species composition in the middle parts of the archipelago was shown. The results, in line with ordination analysis, indicated a seawards shift of the more polluted/impacted zones. The predictive capabilities of the canonical ordination method of redundancy analysis (RDA) were discussed.