Nitrate reductase activity (NRA) was investigated in diferent parts of some Verbascum L. species (Scrophulariaceae) collected from different altitudes of Uludaǧ Mountain, Bursa Turkey. NR activities were compared with respect to (1) different plant organs, (2) different Verbascum species and (3) samples collected from different altitudes (120-1850 m). The highest levels of NRA were found for all species in the leaves. Significant differences were determined between the samples collected from different altitudes. Despite the NRA is the highest in V. olympicum Boiss., it is the lowest in V. lagurus Fisch. & Mey. Furthermore the correlation between NRA values in aboveground organs of species and altitude is significant.