We describe the use of gelatinase standards from human capillary whole blood for calibrating gelatin zymograms. Capillary blood was obtained by fingerstick puncture and prepared in nonreducing Laemmli SDS-PAGE sample buffer without heating. Gelatin zymography revealed that whole blood (0.25- 1 microliter) contained substantial fibroblast-derived (72-kDa) and neutrophil-derived (92-, 130-, and 225-kDa) gelatinases which could be used for calibration purposes. Calibration was linear under different electrophoretic conditions using 6.5-10% polyacrylamide gels containing 1-2 mg/ml gelatin (correlation range, r = 0.990-0.998; perfect correlation, r = 1.000). The use of the standards for characterizing gelatinases from arthritic joint fluid is demonstrated. The standards are easily obtained and well characterized, and should facilitate interlaboratory comparison and standardization.