Total serum immunoglobulin E (IgE) concentrations were determined by a competitive solid phase radioimmunoassay technique in serum samples from patients with a variety of venereal diseases. The mean IgE concentrations for groups of normal persons without venereal diseases was significantly lower then the means for groups of appropriately matched patients with primary syphilis and gonorrhoea. There were also relatively higher IgE values in patients with trichomoniasis. Our data indicate that patients with urogenital infections have higher concentrations of IgE in the serum than matched control patients without such infections.