Children read texts for various reasons. We examined how reading texts for different purposes affected amounts of incidental word learning. Grade 6 students were asked to read texts for fun, to learn about the topic of the text, and for text comprehension. Proportions of words learned incidentally while reading ranged from .06 for free reading to .08 when reading for text comprehension to .10 when reading to learn about the topic. Level of reading ability was a significant factor in all conditions. Low-ability readers hardly learned any words incidentally; high-ability readers defined up to 27 of every 100 unknown words when reading for text comprehension. Implications for future research on incidental word learning and reading instruction are discussed.