The aims of this study were to assess child behaviour in a dental surgery and to isolate the variables most closely associated with lack of cooperation by means of a questionnaire/interview. Sixty-five children aged 6-18 years, who had been referred to one dentist because of poor cooperation, formed the study group. Forty-two children of similar age, treated by the same dentist, but referred for reasons other than lack of cooperation, acted as the control. Assessments of anxiety were made independently by a psychologist who used a number of indices, including the Child Manifest Anxiety Scale (CMAS), Melamed's Child Behaviour Rating Scale and the Venham Picture Scale. Fifty-one children in the study group had experienced a general anaesthetic for dental treatment compared with five in the control group (P less than 0.001). Parents of children in the study group could identify specific instances which contributed to fear of dentistry in 75% of cases. The CMAS found no difference between the groups in general anxiety, but anxiety and cooperation ratings made by parent and dentist in the dental surgery showed significant differences between the two groups, as did the results of the Venham Picture Scale.