1. We evaluated the effect of the local superfusion of prostaglandins E1, I2 and F2 alpha (PGE1, PGI2 and PGF2 alpha, respectively) on rat sciatic nerve blood flow and microvascular resistance. 2. PGE1 increased nerve blood flow (NBF) in a dose-dependent fashion with an EC50 of 10(-6.7) M and an asymptote of 20.1 ml (100 g)-1 min-1. 3. PGI2 increased NBF in a linear dose-dependent fashion, with an EC50 of 10(-5.1) M. PGI2 appeared to be about 1.5 orders of magnitude less potent than PGE1. 4. PGF2 alpha also increased NBF in a dose-dependent fashion. The threshold dose appeared to be identical with PGI2 but may have a reduced capacity of response. The EC50 of 10(-5.8) M was slightly lower than that of PGI2.