The effect of the alendronate (ALD; 30 mg/kg, pH 7.0, p.o.) and sodium nitroprusside (SNP; 10 mg/kg, p.o.; a nitric oxide (NO) donor) on gastric dye retention (GDR) and proximal, medial and distal small intestine dye retentions (IDR) was investigated in rats. The drugs were administered once daily for 4 days. On the last day of treatment, 4 h after ALD administration, GDR and IDR were measured. ALD treatment decreased GDR at postprandial intervals of 20 (28.5%) and 30 min (38.3%), while it increased medial IDR (117.2%), as compared to the saline group. ALD had no effect on dye retention in proximal and distal portions of the small intestine. In 30 min, ALD increased medial (50.5%) and distal IDR (149.7%), as compared to the saline group. Pretreatment with SNP prevented ALD from decreasing gastric retention and intestinal transit. The results of this study indicated that ALD accelerates gastric emptying of liquids in rats and support the hypothesis that the inhibition of nitric oxide is of primary importance.