The effect of High energy shock waves (HESW) on the viability and proliferation of normal human bone marrow cells was evaluated. A dose dependent increase in cytotoxicity with an increase in the number of HESW was demonstrated. In general 700 HESW immediately reduced the cell viability of bone marrow cells by 50%. The CFU-GM assay provides a method to evaluate the effect of HESW on the proliferative capacity of bone marrow. Following HESW treatment the colony forming ability of trypan blue excluding cells also felt in a dose dependent fashion, but some variation in sensitivity was noted. By comparing the sensitivity of various cells, the cells of normal human bone marrow were felt to be less sensitive to HESW effects than those of other tissue cultured cells or malignant cell lines.