Aim: This service evaluation assessed the need for sedation in a population of dental attenders (n = 607) in the North West of England. Methods: Using the novel IOSN tool, three clinical domains of sedation need were assessed: treatment complexity, medical and behavioural indicators and patient reported anxiety using the Modified Dental Anxiety Scale. Results: The findings suggest that 5% of the population are likely to require a course of treatment under sedation at some time. All three clinical domains contributed to the IOSN score and indication of treatment need. Females were 3.8 times more likely than males to be placed within the high need for sedation group. Factors such as age, deprivation and practice location were not associated with the need for sedation. Conclusions: Primary care trusts (PCTs) need health needs assessment data in order to commission effectively and in line with World Class Commissioning guidelines. This study provides both an indicative figure of need as well as a tool by which individual PCTs can undertake local health needs assessment work. Caution should be taken with the figure as a total need within a population as the study has only included those patients that attended dental practices. © 2011 Macmillan Publishers Limited. All rights reserved.