The effects of a combined fixing and decalcifying solution, trichloroacetic acid, on prepared bone marrow specimens were evaluated to try to improve the speed of trephine biopsy processing in our laboratory. The morphological preservation obtained immediately after decalcification was complete was assessed, and also after prolonged immersion in each of two solutions. Trichloracetic acid was made up in the standard manner using distilled water and in an isotonic form by the addition of sodium chloride. Prolonged immersion was performed to assess any possible adverse effects of this acidic solution. By the time decalcification was complete, each solution gave morphological preservation sufficient for diagnostic purposes. However, after prolonged immersion, only the isotonic solution performed adequately.