Hydrographic surveys on the Juan de Fuca Ridge (JdFR) carried out from 1980 to 1987 show a complex pattern of 3He and Mn-rich water column plumes produced by venting from several submarine hot spring areas. In the vicinity of Axial Volcano at latitude 46 ¿N, distinct plumes were detected in 1980, 1982, and 1983 with 3He signatures up to Δ(3He)=64% at ~1500-m depth at distances of ~10 km from the seamount summit. However, the same plumes had no detectable thermal signature, a paradox which is attributed to the high 3He/heat ratios and low salinities of the fluids venting within the caldera of Axial Volcano. Profiles directly over the seamount show hydrothermal 3He in the water column up to 300 m above the caldera foor, with the 3He signal increasing with depth to very high and uniform ratios of Δ(3He)=108--150% below the ~1500-m caldera sill depth. Another apparent locus of hydrothemal input is Helium Basin, a depression on the northeast flank of Axial Volcano which had Δ(3He)=51% when first sampled in 1980. However, subsequent hydrocasts into Helium Basin in 1982 and 1983 yielded lower helium enrichments, suggesting either a decrease in hydrothermal input or flushing of the basin via a mixing event. To the south of Axial Volcano, high Δ(3He) values of ~40% observed over the ridge axis at 45¿18'N and 45¿39'N indicate venting on this previously unexplored section of the ridge. The water column plumes over the U.S. Geological Survey vent site at ~44¿40'N on the southern JdFR have very high Mn/3He ratios of 4600 mol/cm3, and apparently unique characteristic which can be used to distinguish these plumes from those originating at other JdFR vent fields. ¿ American Geophysical Union 1990