Venom‐specific IgE and IgG antibodies were measured in the sera of bee‐venom‐sensitive patients during a 3‐year hyposensitization period. The level of specific IgG antibodies initially increased, and 2 months after the start of therapy, this increase was on average five‐fold. A concomitant hut non‐significant increase in specific IgE antibodies was also observed initially. Later during the treatment period specific IgE antibodies showed a continuous decline and after 3 years the level was one third of the pre‐treatment level. Venom‐specific IgG antibodies, however, remained above the pre‐treatment level. The disappearance of the severe allergic reactions was related to the level of both IgE and IgG antibodies as demonstrated in seventy‐six bee sting challenges. In patients with specific IgG antibody levels above 400 u/ml, no severe reactions were observed even if the patient had levels of specific IgE‐ antibodies of RAST class 3 or 4. These data suggest that the relationship between venom‐specific IgE and IgG antibodies permits an evaluation of the state of immunity to insect stings.