The effect of high ambient temperature on the physical stability and bacterial contamination of 1-L, prefilled, closed enteral feeding systems was examined under simulated clinical conditions. One hundred Jevity Ready-to-Hang enteral feeding systems (Abbott Park, IL, USA) were placed in a 37 degrees C incubator for 24 h. The Ready-to-Hang formula containers were visually inspected at 0 and 24 h. Formula samples were collected from the containers at 24 h and plated on trypticase soy agar. Two samples had insignificant bacterial growth of one colony-forming unit per milliliter that was not demonstrated in repeat culture. No growth was observed for any other sample. Additional samples collected from the two apparently contaminated delivery sets showed no growth. No set showed signs of formula instability, such as coagulation, clumping, or curdling. These findings suggest that, even at a high ambient temperature of 37 degrees C, the risk of bacterial contamination or compromised physical integrity is very low with the use of 1-L, prefilled, closed enteral feeding systems.