This paper concerns the influence of age of acquisition (AoA) in word reading and other tasks, and attempts to develop a number of issues raised by Zevin and Seidenberg (2002). Analyses performed on both rated and objective measures of AoA show that the frequency trajectory of words is a reliable predictor of their order of acquisition, which validates its use as a variable to examine age-limited learning effects. We report a large-scale multiple regression study of French word reading which shows that controlling for cumulative frequency (derived from child and adult frequency counts) does not result in the removal of an effect of AoA in reading aloud French words, but there was no effect of frequency trajectory. We also report some re-analyses of previous published data which show that frequency trajectory has a reliable influence on spoken and written object naming latencies and lexical decision times, but not on spelling-to-dictation or word reading latencies. Cumulative frequency has a reliable effect in all tasks. The methodological and theoretical implications of these findings are discussed.