Glyceraldehyde-3-phosphate dehydrogenase (GAPDH, EC 1.2.1.12) activity and mRNA content is altered in the androgen-responsive human prostate carcinoma cell line LNCaP after exposure to the synthetic androgen R1881. Elevation in GAPDH activity is noted as early as 24 h after treatment with 1 nM R1881 and lasts at least 96 h. R1881 has no effect on the activity of GAPDH in androgen-independent DU145 cells. LNCaP GAPDH mRNA content is lowered by treatment with 1 nM R1881; the magnitude of reduction appears to depend on the length of exposure. The results present at least one means by which androgen-responsive tissues may develop alterations in GAPDH mRNA or activity, as is found in certain tumor tissues.