The distribution of a dermatosis in linear streaks is sufficiently striking to arouse interest as to its identity and origin. The outstanding and most frequent example is naevus unius lateris, but cases of lichen planus and psoriasis with lesions occurring in zoniform arrangement are also well recognized. In instances in which the linear manifestation is but part of a more widespread picture, the characteristics of the generalized eruption make the diagnosis obvious. In cases in which the eruption is entirely zoniform, the morphologic observations may be so characteristic as to make the diagnosis readily apparent clinically. We have observed, however, that in many instances when cases of linear dermatoses are presented before dermatologic societies there is disagreement as to the diagnosis. The discussion of these cases usually includes the consideration of nevus, lichen planus and psoriasis, but at times the evidence presented does not permit the inclusion of the condition