A total of 60 children (mean age +/- SD 7.6 +/- 3.5 years, range 2 - 14.2 years) with recurrent respiratory infections were treated with bacterial wall extract plus bacterial ribosomes (Immucytal) or placebo sprayed into the nostrils and oropharynx three times a day for 1 or 2-week periods over 3.5 months. The treatment was completed by 58 subjects; two patients in the placebo-treated group were withdrawn, one for poor compliance and the other because of headaches. Respiratory symptoms improved from the first month in the Immucytal treated children, but not in the placebo group, with a reduction in the incidence of infections in the upper and lower airways. No changes were noted in respiratory function parameters. Treatment with Immucytal significantly increased serum immunoglobulin A (P less than 0.02) and immunoglobulin M (P less than 0.01) and enhanced skin response to the in vivo lymphocyte blastization test, but there was no significant change in the circulating lymphocyte subpopulations. Both physicians and the patients' parents judged the bacterial extract to be clinically better than the placebo. Immucytal, therefore, may provide a useful alternative therapy for recurrent respiratory infections in infancy.