Cyprinid populations in the Appalachian Plateaus Province of Maryland may be at risk from the effects of acidification because of the high proportion of acid-sensitive streams and elevated levels of acidic deposition within the region. During 1989, we related water chemistry, physical habitat, and watershed characteristics to cyprinid distributions in 56 Appalachian streams in Maryland. These streams were dominated by two cyprinid species, blacknose daceRhinichthys atratulusand creek chubSemotilus atromaculatus. Eleven streams had a pH of 5.30 or less, an acid-neutralizing capacity (ANC) of 50 μeq/L or less, and lacked cyprinids. The remaining streams had a pH of 6.49 or more and ANC value greater than 50 μeq/L, and cyprinids were either absent or present. Streams with pH values 5.30 or less had lower ANC, higher levels of inorganic monomeric aluminum, and lower concentrations of dissolved calcium than high-pH (≥6.49) streams. Chemical characteristics were similar among high-pH streams whether or not they contained cyprinids. Gradient was the primary factor affecting cyprinid distributions in streams that had a pH of 6.49 or more. This indicates that some streams with a pH of 5.30 or less would have lacked cyprinids in the absence of acidification. We conclude that, in Appalachian streams of Maryland, cyprinid distributions are affected by factors related to surface water acidification.