The Swedish Early Communicative Development Inventories (SECDI)--w&g (words and gestures; 8-16 months) and w&s (words and sentences; 16-28 months)--is a new instrument to assess communicative and language abilities in Swedish speaking children. Test-retest reliability and content validity of SECDI were examined. The results show that the SECDI covers common words in Swedish children's vocabulary and that its grammar scale (w&s) incorporates items that develop early among many children. Test-retest was analysed over 2 or 3 months, first for 57 and then for 60 children. Test-retest reliability scores are as follows: SECDI--w&g = between 0.70 and 0.90 in most age ranges; and SECDI--w&s = close to or above 0.90 on most measures.