We have evaluated the yield of several tests and have instituted specimen rejection criteria to reduce costs and save time. For a 12-month period, we recorded the reduction of these tests and calculated the resultant cost and time savings. Seven changes were analyzed: not performing fungal or mycobacterial (acid-fast bacillus) cultures on cerebrospinal fluid (CSF) specimens from patients without known immunosuppression when chemistry and cell count are normal; not performing routine stool culture or ovum and parasite examination on specimens from patients in the hospital for > 3 days; not culturing endotracheal suction aspirates when no organisms or > 10 squamous epithelial cells are present; discontinuing broth cultures on all specimens except for tissue, continuous ambulatory peritoneal dialysis fluid, and CSF from patients with shunts; and eliminating bacterial antigen tests. For each test, the number not performed (n), reagent savings, and technologist time saved, respectively, were as follows: CSF fungal culture, 267, $999, and 67 h; CSF acid-fast bacillus culture, 275, $1,662, and 124 h; stool cultures, 320, $2,991, and 98 h; ovum and parasite examinations, 216, $525, and 108 h; endotracheal suction aspirate cultures, 1,505, $4,447, and 306 h; broth cultures, 5,218, $4,931, and 80 h; and bacterial antigen tests, 2,598, $2,293, and 299 h. Overall, 5,181 tests were rejected and 5,218 broth cultures were omitted. Achievable savings were $28,000 in reagent costs and 1,082 h of technologist time. In conclusion, rejecting specimens of proven low yield saves reagent costs and, more importantly, saves technologist time. This time can be spent on specimens having greater diagnostic utility.