An out-of-hours emergency biochemistry service, which allows access by all medical practitioners of varying experience within a hospital, can lead to overuse or even abuse of limited and costly facilities. When the workload increases, problems of staffing a voluntary (but paid) working rota may emerge. An industrial dispute involving medical laboratory scientific officers (MLSOs) caused the role of the emergency service to be examined and alternative regulating mechanisms to be tested. Experience at Glasgow Royal Infirmary between 1974 and 1981 has been reviewed. From 1977 to 1979, when clinicians (usually junior) arranged analyses directly with the MLSOs, test numbers increased by about 26% per annum. This was not associated with any concomitant increase in the range of analyses offered. During a five-week period in 1980, consultant clinicians had to contact a consultant clinical biochemist to arrange all emergency analyses, and test numbers were reduced to 13% of the previous levels. Subsequently, all requests for emergency analyses were made by clinicians to laboratory medical staff, and test numbers fell to approximately 60% of 1979 levels. This requesting system is now firmly established. Continued vigilance is required to maintain the reduced level of requesting, but too great a limitation on emergency requests may cause less efficient patient management. Senior clinical staff should be encouraged to take greater responsibility for the use of emergency laboratory services.