Immigrants' age of arrival (AOA) in a country where a second language (L2) must be learned has consistently been shown to affect the degree of perceived L2 foreign accent. Although the effect of AOA appears strong, AOA is typically correlated with other variables that might influence degree of foreign accent. This study examined the pronunciation of English by native Italian immigrants to Canada who differed in AOA. As in previous research, those who arrived as young adults (late learners) were somewhat older at the time of testing, and produced somewhat longer English sentences, than those who arrived in Canada when they were children (early leamers). The results of Experiment 1 showed that the greater chronological age of early than late leamers was not responsible for the late learners' stronger foreign accents. Experiment 2 suggested that the late learners' longer L2 sentences were not responsible for observed early-late foreign accent differences. A principle components analysis revealed that variation in AOA and language use, but not chronological age or sentence duration, accounted for a significant amount of variance in the foreign accent ratings. The findings of the study were interpreted to mean that AOA effects on foreign accent are due to the development of the native language phonetic system rather than to maturational constraints on L2 speech learning. © 2006 Cambridge University Press.