We studied the concentration of leaf N and C among 183 fern species along an elevational gradient at 1700 to 3400 m in humid montane forest in the Bolivian Andes at different levels of taxonomic resolution. For two species of Elaphoglossum sampled 8 and 14 times, respectively, there were no elevational trends. Similarly, a contrast of 22 species with wide elevational amplitudes sampled at their highest and lowest locations did not show any change in C or N contents, or in C:N ratios with elevation. At the community level, however, the mean values of C:N ratios for (a) all species found at a given elevation showed a significant decline with increasing elevation and (b) among epiphytic species, higher ratios (i.e., lower relative N content) than among terrestrial species at the same elevation. These trends were opposite to those of the upper soil layer, in which C:N ratios increased with elevation.