A method to detect the presence of Campylobacter pyloridis in dyspeptic patients is described. The test procedure involves placing a gastric pinch biopsy into a small amount of a solution containing urea and a pH indicator in the well of a microtiter tray. The method depends on the ability of C. pyloridis to hydrolyse urea and release an alkaline product (ammonia). The "microtiter biopsy urease test" is 100% specific for C. pyloridis and has a 91% sensitivity after 18 h reaction time. Seventy-five percent of positive biopsies had a reaction time of less than 1 h. The test may be used to predict the presence of antral gastritis; as well as marking the presence of the bacterium; with a positive predictive value of 96% and a negative predictive value of 73%. There was a positive correlation between the biopsy urease test results and the grades of both chronic and active antral gastritis. This test is simple and can be performed in the endoscopy clinic as the formulation of the reagent obviates the need for aseptic techniques.