To describe the development of words and sentences in Swedish children 16-28 months old, 900 parental reports on 336 children were analyzed. Subjects were randomly selected from the national birth register, and there was a response rate of 88%. The assessments were made using the Swedish Early Communicative Development Inventory-words and sentences (SECDI-w&s).

Age-based norms for productive vocabulary, pragmatic skills, grammar skills, and maximum length of utterance (MaxLU) were determined. We describe the development of feedback morphemes, semantic categories, and single words and tasks. Correlation across measures was significant, and especially strong between vocabulary size and grammar skills. Optimized positive predictive values were high for 25 to 28 month predictions (71%-88%), and vocabulary scores were found to be of particular predictive importance. No significant gender differences were detected. The clinical relevance of the instrument is discussed.