An experimental study was conducted on 3 consecutive 12-hour days to determine if selected physical properties of feeding tubes (material and diameter) affect tube clogging. Effectiveness of three irrigant fluids (cranberry juice, Coca-Cola, and water) in preventing tube clogging was studied. One hundred eight tubes were connected to gravity flow feeding bags containing isotonic enteral formula; 54 polyurethane and 54 silicone tubes were equally divided as to external diameters of 8 French (Fr), 10 Fr, and 12 Fr. At 4-hour intervals, flow regulators on the feeding bags were adjusted to a rate of 50 ml/hour. Fluid volumes delivered per minute were measured for each tube at 2-hour intervals. One set of tubes at each station was irrigated periodically with cranberry juice, Coca-Cola, or water. On each of the 3 days, analyses revealed significant, p less than .05, effects for tube material, cranberry juice contrasted with Coca-Cola and water as irrigants, and time. Polyurethane was consistently superior to silicone as a tube material, and cranberry juice was consistently inferior to both Coca-Cola and water as an irrigant. Tube diameter had no significant effect on the incidence of tube clogging.