AIM: To describe changes in infant prelinguistic communication skills between 8 and 12 months, and identify factors associated with those skills. METHODS: DESIGN: Parent questionnaire data for a prospective population-based cohort of infants in metropolitan Melbourne, Australia. PARTICIPANTS: 1911 infants born November 2002-August 2003. OUTCOME: Infant communication (Communication and Symbolic Behaviour Scales (CSBS)) at 8 and 12 months. Potential risk factors: sex; prematurity; multiple birth; sociodemographic indicators; maternal mental health, vocabulary and education; non-English speaking background; and family history of speech-language difficulties. Linear regression models were fitted to total standardised CSBS scores at 8 and 12 months. RESULTS: Social communication, especially the use of gesture, developed rapidly from 8 to 12 months. Female sex, twin birth, and family history were strongly associated with CSBS scores. The combined model accounted for 5% and 6% of the total variation at 8 and 12 months, respectively. CSBS score at 8 months strongly predicted CSBS score at 12 months (coefficient = 0.56, partial R(2) = 37.0). CONCLUSIONS: There is a dramatic increase in communication skills between 8 and 12 months, particularly the development of gesture, which (as in previous studies) predates and predicts future language development. Risk factors explained little variation in early communication trajectories and therefore, based on our findings, this developmental course is more likely to be biologically predetermined. Rather than focusing on risk factors, we suggest that language promotion activities in otherwise healthy young infants should either be universal or, if targeted, be based on the level of communication skills displayed.