Benchmarks for timeliness of early morning routine clinical laboratory tests were developed from over 17,000 urea nitrogen and 16,000 white blood cell count measurements made for inpatients in 653 institutions participating in the College of American Pathologists Q-Probes program. Urea nitrogen and white blood cell counts were considered surrogates for routine chemistry and hematology tests. Laboratories at the 50th percentile reported median urea nitrogen and white blood cell counts by 09.04 and 08.51 h, respectively, whereas those at the 10th percentile reported these median measurements by 11.30 and 11.18 h, respectively. Results were available sooner in non-teaching than teaching institutions, and in smaller rather than larger institutions, with the degree of computerization affecting test availability. Timeliness also was affected by instrument type and mode of operation, but was unaffected by the percentage of stat testing. Based on modeling by regression analysis, there was little evidence that longer routine test turnaround times affect patient length of stay.