Objective: This study was designed to produce a new parent-report measure, the Diagnostic Receptive Expressive Assessment of Mandarin-Infant Toddler Assessment of Communication and Language (DREAM-IT) in order to provide norms for the developmental skills of children aged 0-36 months in four areas: expressive language, receptive language, cognitive play and social skills. Methodology: The scale was designed to be both broader and deeper than existing instruments that neglect one or more of these significant domains involved in early language. Items were chosen by a group of specialists with clinical experience working with the age group and with attention to the developmental literature. Caregivers were tested individually by a trained person who asked the questions and provided examples. In addition to an extensive health questionnaire, caregivers answered questions in Mandarin about their child's behaviour using a scale of 'not yet', 'sometimes' or 'always' or listing out words and/or sounds understood or said by the child. The 476 participating caregivers were recruited at maternal and child healthcare clinics centred in Chengdu, China, 191 of whom were tested a second time seven months later. The children were sampled in three-month age-bands from 0 to 36 months. The sample was balanced for child gender by age band, and parental education was balanced. Caregivers of 0-24-month-old children and caregivers of 12-36 months were each asked a different set of questions, to determine the appropriate age range and cutoff points for each question, requiring the sample size to be doubled for children aged 12-24 months. Results: The results were subject to item-response theory analysis to remove outlying items, and the resulting internal reliability was high for each domain (average Cronbach's alpha=0.87). The final instrument (between 67 and 113 questions in total) was refined to include the least redundant questions that had the highest intercorrelations, with attention paid to coverage of all domains across the age range. Two scales were developed: one for children 0-18 months, the second for children aged 18-36 months. The longitudinal design permitted the creation of growth curves and norms for each domain for six-month intervals from 0 to 36 months. A small sample of 32 parents of children with Down syndrome aged 18-36 months provided validation that the scales are highly sensitive to developmental delay. Conclusion: The instrument shows considerable promise for detecting early communication problems in children in China.