The present retrospective study reviews our clinical experience with Subcutaneous immunotherapy (SIT) over a 10 year period (1981-1991), in order to assess both incidence and clinical features of nonfatal systemic reactions due to this treatment. 192,505 injections were globally administered to 2,206 outpatients, following the suggested precautionary guidelines. We observed 115 systemic reactions (5.2% of patients and 0.06% of injections) and no fatalities. The association asthma + urticaria was the most frequent reaction (67%), followed by asthma alone (22%). No risk factor related to age, gender, pollen season or manufacturer was observed. The occurrence of systemic reactions was highly frequent in asthmatic patients, but approximately 1/3 of the patients who presented reactions had never previously suffered from asthma. The largest part of the observed reactions occurred during the maintenance phase of treatment. Almost all adverse events occurred within 30 minutes after the injection and they were promptly controlled by routine therapy. We conclude that subcutaneous immunotherapy, if performed with careful compliance to good clinical practice rules, is a safe treatment for respiratory allergy.