Five spindle-cell lipomas, all in male patients, were examined by light and electron microscopy. Four were located in the subcutaneous tissues of the upper back or posterior neck and one behind the left ear. They exhibited a spectrum of histological growth patterns. Electron microscopy demonstrated two distinct populations of tumor cells; one, a spindled non-fat-storing mesenchymal cell and the other a mature lipocyte. It is hypothesized that the spindled cells are analogous to the stellate mesenchymal cell of the primitive fat lobule.