Previous studies have examined methods of reducing laboratory use, without great success. We studied the effects of the financial unbundling of clinical biochemistry determinations in a university outpatient clinic. After eliminating the charge structure that promoted panel use, the ordering of chemistry 19 panels fell dramatically, accompanied by an increase in orders for electrolyte and chemistry 6 panels. The total number of biochemical assay determinations fell by one third after this administrative intervention. Only orders for potassium and creatinine measurements remained relatively unchanged and eventually increased. The ordering of five analytes of the chemistry 19 profile was reduced by at least 50%. Reassessment of the intervention six months later demonstrated the sustained decline in laboratory use. We conclude that physicians are attuned to price inefficiencies in basic laboratory testing and can alter their ordering behavior accordingly. Facilities can change patterns of use by altering charge structures alone. The decline in laboratory testing also indicates that physicians receive unnecessary clinical data when they order biochemical profiles. Financially bundled chemistry profiles could be replaced by physiologically based test groupings.