There are no known biomedical or genetic markers to identify which infants with galactosaemia (GAL) are most at risk of poor language skill development, yet pre-linguistic communicative "red flag" behaviours are recognised as early identifiers of heightened vulnerability to impaired language development. We report on pre-linguistic development in two 18-month-old infants with GAL (one of each gender). Results identified the male as displaying significantly poorer pre-linguistic skills than both his matched peers and relative to the female infant with GAL, whose pre-linguistic skills were commensurate with or better than her matched peers. The results suggest that by 18 months of age, differential developmental language skills can be identified in infants with GAL when the focus is on pre-linguistic communication behaviours.