Benthic macroinvertebrates were sampled at 10 sites on small streams in the vicinity of a molybdenum mine and mill in north-central British Columbia, Canada. Invertebrate communities exposed to elevated concentrations of molybdenum and cyanide in drainage from an open pit were taxonomically similar to those in control streams, but had slightly higher species richness and density. Molybdenum and cyanide concentrations in receiving streams were apparently not high enough to adversely affect invertebrate communities.