To determine the optimal conditions for isolation of Campylobacter jejuni from human fecal specimens, we compared incubation atmospheres that contained about 5, 10, and 15% oxygen with the 17% oxygen produced in candle jars and also compared incubation temperatures of 37 and 42 degrees C. At 42 degrees C, C. jejuni was isolated from all 16 specimens; however, colony sizes were larger when plates were incubated in 5 and 10% oxygen than in the other two atmospheres. At 37 degrees C some positive cultures were missed in 15% oxygen and in the candle jar. The largest colony sizes were obtained in 5% oxygen. For each atmospheric condition tested, the colonies were larger at 42 than at 37 degrees C. When incubation is done at 42 degrees C, use of a candle jar is adequate; however, at 37 degrees C candle jars should not be used for isolation of C. jejuni from human feces.