To provide normative data, in the form of percentile scores from a community sample, for the Physical Component and Mental Health Component Summary scores derived from the SF-36, and to provide an example of how to interpret scores on these measures, comparing normative results with data from a clinical sample. Normative data were gained from a postal survey using a questionnaire, containing the SF-36 and a number of other items concerned with lifestyles and illness. The questionnaire was sent to 13,042 randomly selected subjects between the ages of 18 and 64 years, drawn from Family Health Services Authority computerised registers for four English counties. The clinical sample comprised 84 patients aged 18-64 years diagnosed with obstructive sleep apnoea (OSA) who were asked to take part in the study. The Physical Component Summary (PCS) score and Mental Health Component Summary (MCS) score gained from the SF-36 health status measure were the outcome measures. The community survey achieved a response rate of 72% (n = 9332). All 84 patients in the age range 18-64 years approached to take part in the OSA study agreed to do so; complete data were available for 60 patients. Results indicated that, prior to treatment, 75% of OSA patients' scores on the PCS/MCS were less than the standardised mean score of 50 and fell in the lowest 34% of scores in the general population. However, after treatment, over 50% of patients scored above the standardised mean score on both the PCS and MCS and more closely mirrored the distribution of the normative sample. The data provided here should enable a more meaningful presentation of data than is generally provided in research papers presenting SF-36 summary scores.