A study was made of purine receptors (PR) in healthy subjects and bronchial asthma (BA) patients before and after theophylline (TP) treatment. BA patients demonstrated a significant lowering of the binding sites of A2PR and a tendency toward the rise of the number of A1PR on peripheral blood lymphocytes as compared to the healthy subjects. As a result of TP therapy for 3 weeks, the number of A2PR increased in 69% and the number of A1PR fell in 50% of the patients. The efficacy of TP pharmacotherapy depended significantly on the increment of the binding sites of A2PR. The growth of the number of A2PR was recorded in the groups of patients with a beneficial and satisfactory effect of the treatment.