The results of a field and petrologic study of a structurally complicated granophyre-diabase multiple dike from Cape Neddick, Maine, are presented. Although this occurrence shows many attributes of a typical composite dike, detailed evidence indicates that it is multiple in character. Reaction between granophyre magma and brecciated diabase has modified the form of the mass and produced reciprocal changes in the mineralogy. It is shown that, where such reaction has taken place, the absence of chill margins between dike components can be used as a criterion of composite intrusion only with the greatest caution.