A search engine is disclosed that uses correlations between search terms to correct misspelled terms within search queries. The correlations are based at least in-part on historical query submissions to the search engine. Preferably, the correlations reflect the frequencies with which the search terms have historically appeared together within the same query, and are stored within a correlation table using related terms lists. In one embodiment, the correlation table is generated periodically from the M (e.g. 10) most recent days of entries in a query log, and thus reflects the current preferences of users. In operation, when a query that includes both matching and non-matching search terms is submitted to the search engine, a spelling correction process accesses the correlation table to generate a list of terms that are deemed to be related to the matching term(s). The spellings of these related terms are then compared to the spelling of each non-matching term using a spelling comparison function that compares two character strings and generates a similarity score. If a suitable replacement is found for a given non-matching term, the non-matching term is replaced with the similar related term. The modified query is then used to perform the search, and the user is notified of the modification(s) made to the query. In the disclosed embodiment, the search engine is used on the Web site of an online merchant to assist users in locating book titles, music titles, and other types of products.