Studies of patients with atopic dermatitis (AD) have demonstrated several clinical and laboratory indications of immunity defects, but with frequently contradictory results. We have recently shown that many patients with negative cutaneous delayed type hypersensitivity to candidin and streptokinase-streptodornase may have normal in vitro lymphocyte transformation to the same antigens. We hypothesized that this represents recovery of immunocompetent cells when they are isolated in vitro. This report describes phytohemagglutinin-induced transformation of lymphocytes immediately after isolation and after four days in culture (precultured). Responses of lymphocytes from patients with AD were initially subnormal, but increased to normal levels after the preculture period. Our results suggest that defective immune function in AD is not due to a permanent intrinsic lymphocyte defect, but is more likely due to factors associated with disease activity and severity.