Groups of human cholesterol gallstones were subjected to monooctanoin with and without agitation, methyl-tert-butyl ether (MTBE) with and without agitation, and monooctanoin and MTBE used in succession with agitation. In this in vitro study, agitation greatly expedited the rate of dissolution with MTBE, by far the more potent of the two solvents. An additive effect was suggested when the solvents were used sequentially, monooctanoin followed by MTBE. Cholesterol-calcium stones were also dissolved by MTBE but at a slower rate, depending on the amount and distribution of calcium. Computed tomographic (CT) scans and mammographic images clearly delineated the amount and distribution of calcification, but plain radiographs did not. On the basis of these findings, the authors instituted two changes in their clinical protocol: All patients with gallstones are now examined by means of CT before chemical dissolution begins, and monooctanoin is instilled overnight before the MTBE procedure.