This study aimed to investigate the prevalence of sleep problems in Chinese children with pervasive developmental disorders (PDD) in Hong Kong and their relationship to parental stress. A cross-sectional survey was conducted in six child assessment centres. All parents of the children with PDD completed the Children's Sleep Habits Questionnaire, the Parenting Stress Index-Short Form, and questions on sleep practice. A total of 210 out of 250 questionnaires (response rate 84%) were returned. Mean age of the children was 3 years 6 months (SD 1 y 4 mo; range 2 y-7 y 7 mo; 168 males, 25 females). The prevalence of parent-defined sleep problems in various sleep domains ranged from 9.3 to 45.6%, with 67.9% of children having significant problems in at least one sleep domain. The most common problems reported were bedtime resistance and parasomnias. Similar sleep problems occurred in all the PDD subgroups. The factor most significantly associated with sleep problems was the occurrence of sleep problems before the age of 2 years. The parents of children with PDD with sleep problems experienced a higher level of stress than those whose children had no sleep problems. A high prevalence of significant sleep problems was reported in Chinese children in Hong Kong with PDD. A higher stress level among the parents of those children with PDD with sleep problems suggests the need for systematic early detection and management of sleep problems in children with PDD.