After the grounding of the tanker MV Braer off the coast of Shetland an epidemiological study was rapidly instigated to determine any immediate or long-term health effects on the exposed resident population. The study was carried out in two phases, at the time of the grounding and five months later. The objective of this study is to determine the reasons for non-response in both phases of the Shetland Health Study. A telephone survey was performed on a systematic sample of non-responders from the exposed population in both phases of the study. The setting was the south mainland of Shetland. Fifty-nine of the 215 non-responders in the first phase of the study and 16 of the 86 non-responders in the second phase were surveyed. The main reasons for non-response were attitudinal rather than situational or organisational. Non-responders did not feel their health was affected, were not interested in the study or did not think the study was useful. Some were put off by the biological tests involved and some had difficulties with appointment times. Practical issues such as flexible appointment systems are easier to address than client characteristics but factors relating to distrust and indifference must be addressed if non-response rates are to be minimised.