Thirteen cases of acute posterior multifocal placoid pigment epitheliopathy occurred in young adults or older children. In ten there was a characteristic, possibly infectious syndrome that preceded the onset of ocular manifestations by a few weeks. One patient developed cerebrospinal fluid lymphocytosis and a cerebral vasculitis coincident with the ocular changes. Extensive evaluations for viral and other infectious etiologies in this and other cases were unrevealing. An inflammatory reaction was observed in the anterior chambers of most patients, and cells were noted in the anterior vitreous bodies of a few patients. In one instance a serous detachment of the retina occurred adjacent to the optic disk. Our findings and others support the conclusion that the fundus lesions resulted from a multifocal choroiditis primarily involving the choriocapillaris and affecting the pigment epithelium and retina secondarily. The data also suggested that the choroiditis may be associated with a more widespread vasculitis occurring as an immune reaction to an earlier systemic infection.