A picture-word interference experiment examined the origin of the distractor frequency effect, the effect that pictures are named slower in the context of low-frequency than high-frequency words (Miozzo & Caramazza, Journal of Experimental Psychology, 132, 228-252, 2003). We compared two accounts of the effect: an early, input-related account and a late, response-related account. Participants named high and low-frequency pictures with low and high-frequency distractors in two conditions. In the immediate naming condition, picture and distractor were presented simultaneously. In the delayed naming condition, the distractor was presented 1,000 ms after the picture; pictures had to be named upon distractor presentation. There was a distractor frequency effect in both conditions, but an effect of picture frequency only in the immediate naming condition (showing that in the delayed naming condition, lexical selection had been completed). These results support a late origin of the distractor frequency effect.