SUMMARYFive patients with reticular erythematous mucinosis were studied by skin biopsy and phototesting. Light microscopy showed a dermal mononuclear cell infiltrate (composed largely of lymphocytes), separation of collagen bundles and fragmentation of elastic fibres. Histochemical stains showed increased dermal mucin with a profile consistent with hyaluronic acid. In one case, the ultrastructural distribution of mucin was demonstrated using colloidal iron staining, electron microscopy and X‐ray microanalysis. In two cases, virus‐like tubular aggregates were identified in the cytoplasm of dermal cndothclial cells and pericytes. Immunofluorescent staining for immunoglobulins, fibrin and complement was negat