In four rumen-cannulated sheep fed 0, 1.5, 3.0 and 4.5% NaHCO3, the buffer increased rumen pH (P < 0.01) and isobutyrate (P < 0.10) but not rumen ammonia, lactate or other volatile fatty acids. Water intake increased (P < 0.01), liquid turnover rate varied quadratically (P < 0.09) and solids retention time and rumen solids volume varied cubically (P < 0.09 and P < 0.01) with NaHCO3 levels. Key words: Sodium bicarbonate, liquid turnover rate, solids retention time, sheep