The clinical and immunologic efficacy of venom immunotherapy up to 50 micrograms maintenance doses (half the recommended dose) was examined in 23 patients with anaphylactic sensitivity to insect stings and is compared with that in two groups of patients treated with the full 100-micrograms recommended dose. Four of the 19 patients challenged with insect stings had mild systemic reactions not requiring treatment. This 79% clinical efficacy is significantly less than the 96% to 100% success achieved with treatment to full 100-micrograms maintenance doses. The venom-specific IgG antibody response to the 50-micrograms dose reached a level significantly lower than observed with 100 micrograms doses. We conclude that the clinical and immunologic responses to venom immunotherapy are dose dependent and are more reliably complete at the recommended maintenance dose of 100 micrograms of each venom than at a dose of 50 micrograms.