A review of ordering patterns for thyroid function tests and for measurements of creatine kinase (CK) isoenzyme and lactate dehydrogenase (LDH) isoenzyme levels indicated considerable misuse. We employed an educational program for both types of tests, but changed the request form only for ordering the thyroid function tests. No changes were made in the forms for ordering CK and LDH isoenzyme tests. The effect was a prompt decrease in ordering triiodothyronine radioimmunoassay and thyrotropin tests to 38% and 61%, respectively, of baseline rates. There was no effect on rates of ordering CK and LDH isoenzyme tests, which were 102% and 96%, respectively, of baseline rates. The improved use of thyroid function tests was likely because of the change in the laboratory request form, since the educational strategy by itself had no effect on the ordering of CK and LDH isoenzyme tests.