"Undifferentiated" neuroblastoma glioma hybrid NG 108-15 cells have not previously been characterized at a light and ultrastructural level despite their use in opiate receptor studies and their possession of one or more opioids. Three cell types rather than one were found. Type A is the classic round hybridoma cell. Type B is a neuron like cell and Type C is a giant cell similar to Type A cells but larger and with dense cytoplasm. Dense core vesicles, 800-1200 Ao in diameter were found as were virus particles in most Type A cells. Multivesicular bodies with clear vesicles which are interpreted as glutaraldehyde artefacts were found but no clear neurosecretory vesicles were found in any A cells--Etorphine at 10(-6) M for 48 hours and naloxone 10(-4) M were employed to product dependence and precipitated abstinence but no clear cut morphologic differences were noted between control, opiate dependent and precipitated abstinent cells.