The incidence of contact-allergic reactions to some 10 substances out of 75 tested in 100 selected leg-ulcer patients is about 5 times as high as in eczematous patients. These substances are p-phenylenediamine, p-aminoazobenzene, Pellidol®, benzocaine, diaminodiphenylmethane, neomycin, coal tar, balsam of Peru, wool alcohols. Sesame oil was the tenth substance. It is used to clean the skin from rests of ointments. In Holland it figures as a constituent of the often-used, so-called pasta zinci oleosa, ung. diachylon, ung. simplex, and of emulgide cream. In our opinion, not only topical medicaments should be regarded as frequent contact sensitizers in leg-ulcer patients. A second class of important sensitizers in this group of patients appears to be the para-substituted substances such as p-phenylenediamine (and azo dyes) as inducers considered to be responsible for the cross-reaction of drugs such as benzocaine and sulfanilamide, and of the rubber additive, diaminodiphenylmethane. Stress is laid upon five preventive measures concerning contactants in leg-ulcer patients (stockings, bandages, topical medications) and upon the desirability of having non-sensitizing preservatives and stabilizers at one’s disposal–especially for topical medications in leg-ulcer patients who apparently are sensitized with greater ease than patients with other skin ailments.