Cutaneous lesions caused by the pine processionary caterpillar Thaumetopoea pityocampa (TP) are frequent in pinewood areas. In the present study, 30 patients diagnosed with occupational immunologic urticaria from this caterpillar were included. Immediate hypersensitivity was demonstrated by performing prick and IgE-immunoblotting tests. Workers were grouped according to their common tasks. Occupations at risk of exposure to TP were pine-cone collectors/woodcutters (14), farmers/stockbreeders (8), other forestry personnel (4), construction workers (2), residential gardeners (1) and entomologists (1). Besides contact urticaria, angioedema (60%), papular lesions of several days of evolution (30%) and anaphylactic reactions (40%) were also detected. The most frequently detected molecular weight bands by immunoblot were 15 (70%), 17 (57%) and 13 kDa (50%). The appearance of isolated bands corresponds with the least serious cases. Only 8 subjects had bands higher than 33 kDa, which was present in the 3 most severe cases of anaphylactic reactions. By presenting these cases, we wish to offer the largest series reported so far of occupational immunologic contact urticaria caused by TP. We include the first cases described in certain occupations, some of them not directly related to forestry work. Pine-cone or resin collectors, woodcutters, farmers and stockbreeders were the most frequently and severely affected workers.