A prospective investigation of the impact of ingested liquids on 24-hr pH test scores was conducted. Eighty-two patients contributed 142 samples. The liquids used were coffee/tea (N = 35), water (N = 32), fruit juice (N = 29), cola (N = 34), and beer (N = 12). The pH of cola, juice, and beer are approximately 3.0. The parameters studied included: total test time, total drink time, total minutes of pH < 4.0 during drink, minutes of < pH 4.0 10 min before drink, and minutes of pH < 4.0 10 min following drink. Analysis was performed using one-way ANOVA and repeated measures. Age of patients, total test time, and total time pH < 4.0 were not significantly different (P > 0.05). The total time to consume the drink was significantly greater (P < 0.05) for beer than all other liquids. The total time (7.7 +/- 6.0 min) pH < 4.0 for cola was significantly different (P < 0.023) than beer (3.3 +/- 3.7 min), tea/coffee (1.4 +/- 6.5 min), and water (1.1 +/- 2.5 min). The percentage of total time pH < 4.0 was not significantly different (P > 0.05) among any of the liquids. The percentage of time pH < 4.0 during the drink was the highest for cola (63 +/- 47%) and juice (51 +/- 57%); water, coffee/tea, and beer were not significantly different (P > 0.05). Although the impact of cola and juice were the greatest, none of these had an impact that exceeded 0.5%. The lack of impact of beer appears to be due to the increased period of time it takes to consume. We conclude that the impact of ingested fluids is minimal and can probably be disregarded in most patient groups.