A nearly three-year-old boy with a genitourinary malformation, which had already been operated on several times, developed generalized urticaria, facial swelling and bronchospasm within 15 minutes of the induction of anaesthesia. The signs quickly responded to the administration of methylprednisolone (32 mg), clemastine (10 mg) and ranitidine (25 mg). There was a twofold positive immediate reaction in the prick test to natural rubber latex (white and brown), and specific IgE was demonstrated against the latex (2.58 kU/l). On the other hand, prick tests with perioperatively administered drugs and an oral provocation test with an antibiotic administered in the perioperative period were negative. The history of itching caused by an indwelling bladder catheter, vesicles on the lips after sucking on a rubber dummy and the described findings on examination both point to the natural rubber latex as the responsible allergen. No complications occurred three months later during a surgical intervention under administration of steroids and H1- and H2-receptor antagonists, as well as avoidance of materials made of natural rubber latex.