Despite widespread fecal blood testing, the technique of gathering stool for sampling has remained uncontrolled. We sought to describe how patients have contended with this awkward step, to study artifact caused by toilet water, and to construct a collection device that prevents sampling problems. A survey of 250 patients showed that most (56%) had retrieved stools from the toilet basin, 17% used a pan or other household receptacle, 10% used newspaper or tissue paper, and 17% had been unable or unwilling. Sampling stool from the toilet basin introduces error because 4% to 75% of blood leaches from the fecal surface into surrounding water after only 4 to 12 minutes, and many toilet sanitizers cause false-positive guaiac reactions. We describe an inexpensive, disposable stool collector; outpatient compliance has been 97% using this device. To avoid biochemical artifact and facilitate stool sampling, we advocate that a collection device be incorporated into the occult blood testing process.