Two groups of subjects were immunized with combined vaccine containing aluminum hydroxide-adsorbed botulinum toxoids, types A, B, and E, and 4 mld of formaldehyde-inactivated V. cholerae Inaba and Ogawa organisms. The first group included laboratory workers who were previously immunized against cholera and had professional contact with botulinum toxins and viable V. cholerae organisms. The second group included young men who were never vaccinated against botulism or cholera. The three-dose immunization schedule with combined vaccine resulted in clear-cut antitoxin response; after the third dose, the A, B, and E antitoxin level ranged from 0-2 to 10 IU/ml. Immunity against botulinum toxins lasted at least one year. Distribution of the antitoxins among IgM and IgG globulin classes resembled that in the case of response to other toxoids; 21 days after the third immunization antitoxin activity was found in IgG globulins.