A revised form of MacArthur-Bates Communicative Development Inventory III (SCDI-III) was presented designed for Swedish speaking children aged 2 years 6 months–4 years 0 months with the objective to give a proxy measure of their language competence. The instrument contains a vocabulary checklist with 100 words, mainly predicates, from four areas; Food words, Body words, Mental words and Emotion words. Two sections assess the child’s grammar skills and a final section appraises the child’s metalinguistic awareness. Assessments from 1,134 parents are reported. Scales with adequate psychometric properties were formed for each section. Monthly median values and spread of score distributions are presented for each scale. Girls scored higher than boys on all scales. The revision, sampling procedures, demographic variables and issues of reliability and validity, are discussed. The general structure of the instrument can well be integrated in similar instruments designed for other languages and cultures.