Skin test reactions were evaluated in 242 patients who appeared to develop delayed type drug eruptions from the clinical course. The patch testing was positive in 62 (31.5%) of 197 patients tested and the intradermal testing in 105 (89.7%) of 117 patients. The positive ratios of intradermal testing were higher in maculopapular (MP), erythema multiforme (EM), and erythrodermic (ED) types than in eczematous (Ecz) type drug eruptions, while those of patch testing were comparatively high in ED, Ecz type, and anticonvulsant-induced drug eruptions. It is considered that the combination of patch testing and intradermal testing is useful for determination of causative drugs in delayed type drug eruptions.