Assessing infant pain for clinical or research purposes is challenging because infants are unable to talk about their pain. However, infants can communicate distress and pain in a number of ways, including facial activity, body movement, crying and changes in physiological responses. Rami Nader is studying how pain expression changes during the first year of life, when infants undergo a particularly rapid rate of growth and development. He is also investigating the link between parents’ assessments of pain and factors that influence those assessments. Improved understanding of how infant pain expression changes and what influences parents’ reports of pain will contribute to refinement and development of more developmentally appropriate measures of pain.