Fecal diversion has been implicated as an etiologic factor in anastomotic stenosis following colorectal surgery, particularly following the use of circular anastomotic stapling devices. However, experimental confirmation of the effects of fecal diversion on anastomotic healing is virtually nonexistent. The purpose of this study was to serially evaluate colorectal anastomotic healing with proximal colostomy (COL) and without it (CON; control) using two anastomotic techniques in a porcine model. Fifty-two (28 CON; 24 COL) mixed-breed female pigs had colorectal anastomoses using either a two-layer handsewn (HS) or an EFA®(U.S. Surgical Corporation, Norwalk, CT) circular stapled (CS) technique. Anastomotic blood flow was measured using laser Doppler velocimetry (LDV). At second surgery (5, 11, 60, or 120 days post-operatively), the following data were collected: repeat LDV, gross and microscopic anastomotic inflammatory scores, anastomotic diameter, and bursting pressure. There were no significant differences in anastomotic blood flow (LDV), inflammatory scores, or incidence of leak or stenosis between the CON and COL groups or between anastomotic techniques. Bursting pressure was significantly lower for the COL group at day 11 but not any other postoperative day (POD). Proximal colostomy does not appear to exert adverse effects on colorectal anastomotic healing. The choice of colorectal anastomotic technique should not be influenced by the need for proximal colostomy. © 1992 American Society of Colon and Rectal Surgeons.