This paper presents the design and implementation of a spelling checker for Turkish. Turkish is an agglutinative language in which words are formed by affixing a sequence of morphemes to a root word. Parsing agglutinative word structures has attracted relatively little attention except for application areas for general purpose morphological processors. Parsing words in such languages even for spelling checking purposes requires substantial morphological and morphophonemic analysis techniques, and spelling correction (not addressed in this paper) is significantly more complicated. In this paper, we present the design and implementation of a morphological root-driven parser for Turkish word structures which has been incorporated into a spelling checking kernel for on-line Turkish text. The agglutinative nature of the language complex word formations, various phonetic harmony rules, and subtle exceptions present certain difficulties not usually encountered in the spelling checking of languages like English and make this a very challenging problem. © 1993 Oxford University Press.