A 52-year-old male patient with generalized eruptive histiocytoma persisting for about 20 years is described. The clinical picture is characterized by red-brownish, round to oval nodules histologically consisting mainly of histiocytes. The ultrastructure of these skin lesions shows histiocytic cells at various stages of differentiation with different degree of lipid storage. The generalized eruptive histiocytoma are separated from multicentric reticulohistiocytosis. The significant differences refer to the clinical picture, in particular the organ manifestations associated with the skin lesions. The histological and ultrastructural features of the generalized eruptive histiocytoma differ from this differential diagnosis for lack of giant cells and of interdigitations between the neighbouring cells. The relation between generalized eruptive histiocytoma and the multinodular reticulohistiocytosis is discussed.