Solutions of bupivacaine precipitate when bicarbonate is added. This limits the clinical use of pH-adjustment in optimizing bupivacaine activity. In this study four different bupivacaine solutions were studied with the addition of sodium bicarbonate at 4 degrees C or 20 degrees C. Bupivacaine concentrations remained unchanged after pH-adjustment. Least crystallization was observed with bupivacaine solutions containing a small amount of sodium bicarbonate and stored at 4 degrees C.