We investigated how letter length, phoneme length, and consonant clusters contribute to the word length effect in 2nd- and 4th-grade children. They read words from three different conditions: In one condition, letter length increased but phoneme length did not due to multiletter graphemes (H"aus"-B"auch"-S"chach"). In the remaining conditions, phoneme length increased in correspondence with letter length. One presented monosyllabic words with consonant clusters (He"rbst"); the other presented disyllabic words without consonant clusters (Kö.nig). Phoneme and letter length contributed to the length effect in naming latencies. Words with consonant clusters elicited the largest length effect. We interpreted this finding as reflecting difficulties of young readers with accessing the output phonology of the tightly coarticulated consonant clusters from the separate phonemes delivered from serial grapheme-to-phoneme conversions. Moreover, eye-movement data indicated that increased reading speed, accompanied with decreased word length effects, is due to more efficient grapheme-to-phoneme conversions rather than the emergence of whole-word recognition.