Examined (a) the impact of demographic, medical, and psychological factors on overall child distress during an invasive medical procedure required for pediatric cancer treatment and (b) the relationship of individual parent behaviors to child distress across phases of the procedure. Seventy 3- to 10-year-old pediatric cancer patients receiving outpatient venipuncture and their parents participated. Overall distress was greater in younger children who had fewer previous venipunctures and poorer venous access and whose parents rated them prior to the procedure as less likely to be cooperative. Providing explanations regarding the procedure was the parent behavior most clearly associated with child distress. The impact of parent explanation depended on when the explanation was given and on the child's level of distress at the time.