Laser photocoagulation was applied in vitro to organ culture exoplants of porcine retinal pigment epithelium (RPE) attached to Bruch's membrane. Four-millimeter-round buttons of eye wall containing RPE, choroid, and sclera were treated with 25 spots from the argon blue-green laser using 300 mW of power, a 500-micron spot size, and 0.1-s duration. Laser photocoagulation disrupts individual RPE cells acutely and lifts damaged RPE cells from Bruch's membrane. Treated areas become covered with irregular mounds of RPE cells within seven days. The acute damage and subsequent repair of the RPE in organ culture mimic the response of the RPE following laser photocoagulation in vivo. Thus, the morphologic response of the RPE to laser photocoagulation is an intrinsic property of this tissue that does not depend on the presence of the overlying retina.