The spectrum of language regression in childhood is incompletely understood. To describe the features of this disorder more fully, we reviewed the records of 196 consecutive children (143 males and 53 females) with language regression or perceived plateau evaluated between 1988 and 1994 by a child neurologist. Mean age at regression was 21.2 months and the mean interval to referral was 34.8 months. A trigger for the regression was identified in 74 of the children (38%) and was associated with a more rapid regression. Mean age at follow-up was 64 months (SD 55). Seventy per cent of the children became nonverbal, and 75% were cognitively impaired. Language regression was associated with a more global autistic regression in 93% of children. There was a history of seizures in 15% of the children. Some recovery occurred in 61% but only one child recovered fully. Improvement was more likely in the 49% who were entirely developmentally normal before the regression. We conclude that language regression in childhood is a serious disorder with significant long-term morbidity.