A PDA (personal digital assistant) program containing information on 193 laboratory tests was provided to students during the 8-week core clerkship in internal medicine. Students used the program at their own discretion. The number of times each test was accessed during the clerkship was recorded by the program's database. Ten tests were accessed by more than 40% of the students: serum enzymes (lactate dehydrogenase, amylase, alkaline phosphatase, creatine kinase, and gamma-glutamyl transferase), electrolytes (sodium and potassium), renal function tests (urea and creatinine), and a plasma protein (albumin). The most frequently looked up test category was the CBC, followed by liver-related tests, plasma proteins, electrolytes, and autoantibodies. Students at the 2 hospitals where the clerkship was offered had similar test lookup patterns. We conclude that students seek information about laboratory tests that are frequently ordered and directly relevant to the diagnosis and management of their patients.