We prospectively assessed serum lactate and plasma HIV viral load in 20 patients with stavudine-related nucleoside neuropathy, 10 with HIV-related distal sensory polyneuropathy (DSPN), 20 receiving stavudine but without neuropathy and 23 not receiving stavudine and without neuropathy. Raised serum lactate levels discriminated between stavudine nucleoside neuropathy and DSPN with 90% sensitivity and 90% specificity (P = 0.001). DSPN occurred despite an undetectable viral load, making it a poor discriminator.