We examined whether protein kinases have a role in the expression of anaphylactic shock (AS). Guinea-pigs sensitized to ovalbumin were administered i.p. saline (control) or 10 micrograms/kg K252a, a potent protein kinase inhibitor, 30 min before challenge. The development of AS and mortality was observed for the next 2 h. In the K252a-treated group the incidence of AS fell to 53% from 100%, the maximum intensity was 62% less than the control, and mortality dropped to 16% from 50% of the animals. We suggest that protein kinases are involved in the expression of AS, and that inhibitors of these enzymes may protect against the symptoms of AS and allergy.