Macroalgal distribution varies with prevailing environmental gradients in fjords, particularly in glacial fjords such as Kongsfjorden, Svalbard. This survey by scuba diving in 1996 and 1998 was the first to determine species composition, dominance and distribution of macroalgae along the entire length axis of a fjord in the Arctic. Macroalgal distribution was determined quantitatively by frame sampling and with digital video along transects at five hard-bottom locations from outer to inner fjord and interpreted against environmental gradients of depth (0-30 m), substratum, wave exposure and distance from inner glacial front. Most species identified (>70 %) belonged to the Arctic and Arctic-temperate biogeographic groups, often with limited distribution to inner or outer part of the fjord. Dominant species or species with wide geographic distribution were typically widely distributed along the fjord axis. Peaks in biomass varied from 5-10 m at the middle to outer fjord, whereas in the inner bay it peaked at < 5 m. The biomass distribution of macroalgae was mainly related to depth and distance from the inner glacial bay, and varied with wave exposure and sediment cover. Climate-related changes, after our study, indicate that the macroalgal belt has become shallower at Hansneset in middle fjord, with increased biomass in the upper sublittoral zone because of higher temperature and less sea ice. Distribution and production of macroalgae and fauna in shallow regions of the Arctic are likely to increase in the future, particularly in areas subjected to ocean warming, such as Kongsfjorden and other fjords and coastal areas in Svalbard.