An instrument employing saline lavage with simultaneous suction has been devised. This instrument can assist in a) maintaining optimal visualization free of obscuring debris or hemorrhage and b) obtaining material for cytologic examination from the visualized 25-cm length of rectosigmoid and the more proximal bowel. Experience to date reveals excellent correlation of histologic and cytologic diagnoses for lesions within range of the proctoscope and for strictures in which roentgen and biopsy data are inconclusive. A high degree of accuracy (75%) has been demonstrated for sigmoid and left colon lesions. The technic is suitable for the general population as well as those with a higher risk of malignant degeneration (to facilitate the early diagnosis of cancer). Physician time and patient discomfort can be kept to a minimum, and the technic may be applicable as an office procedure.