In their paper published in BMC Oral Health in March, Barker and Horton present qualitative data which explored Latino parents' main concerns regarding accessing dental care for their pre-school children. In the radical discourse of health promotion the use of participant narratives is a first and essential step in community development interventions. While there is agreement regarding the development and implementation of health promotion, the means by which it is evaluated or the type of evaluation design used, is hotly debated. This commentary outlines the rationale of adopting a randomised controlled trial methodology, contrasts it with realistic evaluation and considers design evaluation in the light of the Medical Research Council's (MRC) guidance of 2000 and 2008. It is at this juncture that the commentary suggests that, despite the MRC's acknowledgement of the limitations of its 2000 guidance, there remains, in the 2008 guidance, an underlying insistence to use design evaluations which control for selection bias and confounding extraneous factors. For the evaluation of health promotion interventions it may remain a case of fitting a square peg into a round hole.