This study was a pilot investigation of the initial validity of a newly developed behaviour-screening instrument for early intervention service providers. Group Special Education, Early Intervention (GSE/EI) (2005) adapted the Canterbury Behaviour Screening Protocol (CBSP) from a widely used behaviour-screening instrument the Early Screening Project. The CBSP consisted of 49 items in 2 checklists. GSE/EI identified 10 early childhood centres with a total roll of 712 to participate in the study. Staff were asked to categorise children's problem behaviours as either withdrawn/isolated or aggressive/oppositional, using profiles provided. Next, they were asked to nominate 2 children in each category, and an additional 2 children in either category, and to rank them from most concerning to least concerning. Centres identified 25 children in the withdrawn/isolated category, and 28 children in the aggressive/oppositional category. Staff completed checklists for children with parent/carer consent, which were scored according to preset protocols. Scores on the CBSP were assigned risk values ranging from "extreme" to "no risk". The estimated prevalence of "high" to "extreme" behaviour problems was 7.2% based on CBSP protocols and teacher nominations. The level of agreement between teacher rank and CBSP score was 79%, and this determined the initial specificity. Next, independent observations of the behaviour of the nominated children were conducted during free play periods at the centres by an observer blind to the children's nominated category, teacher ranking or checklist score. Risk levels were assigned based on the observation scores, using a cut-off value of 37% time spent in problem behaviour for girls and 40% for boys. There was agreement in terms of teacher rank and observation scores, (categorised into either "no risk" and "at/high/extreme risk) for 65% for children in the withdrawn/isolated category, and 75% for children in the aggressive/oppositional category. The level of agreement between the CBSP score and the observations (categorised into either "no risk" or "at/high/extreme" risk) was 40% for children in the withdrawn/isolated category, and 46% for children in the aggressive/oppositional category. Using the cut-off values, a prevalence estimate for high risk or extreme risk for behaviour disorders, based on independent observation of children, was 3.2%. Centre staff completing a feedback form determined the social validity of the CBSP. Although responses were generally favourable, a number of suggestions were also made to improve the procedure. Despite limitations in the design of the draft, the CBSP shows promise for a first step in a screening procedure designed to screen New Zealand early childhood centres for children who may be at risk for developing behaviour and/or social emotional problems. The independent observation may also be useful as a second step, prior to extensive eligibility assessment. A number of suggestions were made for future drafts such as addressing the limitations specified, conducting the CBSP with a greater number of children, and determining the concurrent validity, and test-retest reliability.