This study examined the effect of secondary transport on critically ill patients and the effectiveness of a regionally based intensive care service. Four hundred and ninety-five patients were studied retrospectively over a 2-year period. Eighty-two were transferred from peripheral hospitals in a mobile intensive care unit while the remaining 413 were admitted directly to the intensive therapy unit at the Western Infirmary, Glasgow. The severity of illness in both groups was assessed using the APACHE II scoring system. The transferred group were scored before and after the journey, while the directly admitted group were scored only on admission. The results show that the transferred patients exhibited a consistent cardiorespiratory response to transport irrespective of their severity of illness, and that the mortality in both groups of patients in the intensive therapy unit was not significantly different. The results also suggest that in the transferred group, the outcome is not only dependent on the severity of illness but also on other factors, such as the hospital from which the patient was referred and the duration of the pretransfer admission.