There are large differences in the use of laboratory tests between hospitals in Sweden. These differences are not only due to differences between the patients treated but also to differences in practice. Use of laboratory test seems to reflect local traditions to a large extent. These large variations in practice are not compatible with the objective of providing care on equal terms and reduce the cost-effectiveness of clinical chemistry. Recently, several intervention studies have been performed in Sweden with the aim to optimise the use of clinical chemistry tests in primary care. The results show that it is possible to reduce the cost in primary care by SEK 100 million per year while increasing the clinical usefulness. This constitutes approximately 10% of the total cost for clinical chemistry tests in primary care. It should also be possible to reduce the cost for clinical chemistry tests in secondary and tertiary care. Hospitals order more tests than primary care and the potential savings are thus greater. We have studied the ordering habits for eleven Swedish hospitals. The comparison was made in the form of ratios between related laboratory tests to reduce the effects of differences in size between the studied laboratories. The large variation between hospitals indicates that a continuous discussion between the clinicians and the laboratories could reduce the cost. We have used the figures from the comparison and calculated the potential savings for seven frequently used tests. The potential yearly saving in Sweden for these tests is approximately SEK 150 million.