Fifty-six patients with serologically confirmed bee sting hypersensitivity were treated for 1-3 years with either bee venom (BV) (31 patients) or wholebody extract (WBE) (25 per cent of re-exposed patients on BV-therapy showed a diminished reaction and 75% no reaction. Thirty-three per cent of re-exposed patients on WBE-therapy developed an unchanged or worse reaction, 42% a diminished reaction and 25% no reaction at all. An initial rise in BV-specific IgE was observed in BV-treated patients, whereas IgE levels after 1 year of treatment lay significantly below pretreatment values in both treatment groups. BV-specific IgG increased markedly in patients on BV-therapy and decreased slightly in those on WBE-therapy. The initial IgE increase induced by BV-therapy was insignificant in patients with high pretreatment levels of specific IgG-antibodies. Similarly, re-exposed patients with high BV-specific IgG showed no IgE increase, whereas a substantial rise in specific IgE was observed in those with low IgG. On the basis of clinical and serological results immunotherapy with BV is considered to be clearly superior to immunotherpy with WBE.