We studied the medical histories of 127 patients diagnosed with multiple myeloma included in a population-based registry of 945 patients with a para-protein or multiple myeloma in the region of the Comprehensive Cancer Center West (CCCW). We defined patients "not immediately diagnosed" or "delayed diagnosis" as those patients in whom myeloma was not included in the initial differential diagnosis. We found that 37% belonged to this category. These patients more often had symptoms not associated with multiple myeloma. Since a surprising 51% of patients with delayed diagnosis turned out to have stage-III myeloma, the physician should be alert to the presence of this disease, despite the fact that co-morbidity may mask its presence.