In this follow-up study, we evaluated children's communication development at the ages of 8 ("n" = 50), 18 ("n" = 46), 24 ("n" = 44) and 36 months ("n" = 36) using the Finnish version of the "MacArthur Communicative Developmental Inventories" (MCDI). A sample of children ("n" = 14) received family-based intervention 10 times in five months and mother-infant relationship was examined using the "Parent-Child Early Relational Assessment" (PC-ERA) before (at the age of 9-12 months) and after (at the age of 15-18 months) the intervention. The infants' communication skills developed from the use of few words and signs of understanding to that of longer sentences and better grammar during the study period. Specifically, girls scored higher than the boys on the 24-month MCDI. Eight-month-old infants with siblings in the family were more competent than those without siblings, measured using the PC-ERA "infant" variables. However, there were no significant differences in the MCDI or PC-ERA scores between children with and without intervention. (Contains 3 tables and 2 figures.)