Seventeen patients having a posterior uveal melanoma underwent enucleation following documentation of tumor growth. Duration of follow-up from diagnosis to enucleation ranged from 3 weeks to 30 months. The mean rate of enlargement in cubic tumor volume was 56.3 mm3/mo for eight spindle cell melanomas and 270.3 mm3/mo for nine mixed cell melanomas. The mean tumor doubling time calculated according to the exponential growth equation was 291.6 days for the eight spindle cell melanomas and 128.2 days for the nine mixed cell melanomas. The mean mitotic activity was 3.5 mf/40 hpf for the eight spindle cell melanomas and 5.4 mf/40 hpf for the nine mixed cell melanomas. These results suggest that mixed cell posterior uveal melanomas generally grow faster and have shorter doubling times than do spindle cell melanomas.