Because children with intellectual and developmental disabilities (IDD) are frequently unable to report their pain verbally, parents often serve as proxy reporters in interpreting and describing their child's pain. Although there is substantial evidence that interactions among biological, psychological, and social factors at the level of both the child and the parent influence children's behavioral pain expression and parents' interpretation of pain behavior in the general population, there has been almost no work investigating the influence of dyadic parent-child relationships on pain assessment among children with IDD. The long-term goal of this project is to improve the understanding of dynamic and reciprocal processes influencing how parents rate and respond to pain in children who have difficulty expressing themselves verbally due to IDD and who may exhibit idiosyncratic pain signs. To achieve this end, the short-term goal of this project is to identify the specific parent and child factors associated with pain expression among children with IDD and differences in parental pain intensity ratings. The project will achieve this objective by recruiting a large sample of parent-child dyads in which the children are between the ages of 1.5 and 5 years and have been diagnosed with global developmental delay (GDD). Dyads will be video recorded during a clinically-indicated blood draw to evaluate pain expression, parents' pain intensity ratings, and parental behaviors during the pain event. Information on parents' overall judgments of their children's pain sensitivity will also be collected. We will collect information on the children's adaptive behavior, communication abilities, and gross motor function, as well as several standardized rating scales to categorize parents' general negative affect and pain-related beliefs and cognitions. Completion of the proposed project will lead to improved understanding of how parent-child factors interact to influence parents' judgments of pain among children who cannot self-report.