Some damaging effects that occur during cryopreservation by freezing to -196 degrees C have been evaluated in rabbit taenia coli by analyzing the proportional recovery of acetylcholine- and histamine-induced maximal contractions. Dimethyl sulfoxide (Me2SO) 10 v/v% was used as the cryoprotectant; it reversibly abolishes spontaneous contractility even after incubation at 37 degrees C during 2 hr. Programmed freezing at 0.6 degrees C/min with compensation for the latent heat of fusion and warming at 35 degrees C/min proved to be slightly superior to programmed cooling without compensation and slower warming. The degree of functional recovery was comparable after either abrupt or stepwise removal of Me2SO. Freeze-thawing resulted in a significant reduction of contractile force in each buffer solution tested, and acetylcholine-induced contractility was always better preserved than histamine-induced contractility. The best preservation (approximately 65%) was obtained in a potassium-rich buffer solution. The absence of calcium and magnesium from the incubating medium had no influence, whereas the presence of EDTA significantly affected functional recovery. It is difficult to compare our results with those reported by others because of multiple methodological differences. However, it seems that previous results can be improved by changing the freezing rate and the composition of the incubating and cryoprotecting medium.