Intraglomerular coagulation and fibrinolysis could be involved in the exacerbation of renal diseases, and urinary fibrin/fibrinogen degradation products (FDP) may be applicable as an index. Although the urinary FDP can be estimated by the latex agglutination method, this technique has disadvantages such as a poor sensitivity and is of the semiassay type. Recently, a new method of measurement which improves on these disadvantages, termed the latex photometric immunoassay (LPIA) method, has been developed. However, since FDP measurement by LPIA was designed for the purpose of serum FDP estimation, a measurement technique for urinary FDP has not yet been established. The purpose of the present study was to devise a measurement procedure for urinary FDP employing the LPIA method, and to obtain data on the normal levels of urinary FDP in healthy subjects. The results obtained may be summarized as follows. (1) The urinary pH and coexistent substances such as bovine serum albumin, glucose, urea, bilirubin, ascorbic acid, and hemoglobin, did not influence the urinary FDP measurement. (2) No changes in urinary FDP were observed after 28-day storage at -20 degrees C or -80 degrees C in the presence or absence of tranexamic acid. (3) The coefficient of variation was 5.3%. (4) The normal level of FDP excretion was 3.33 +/- 7.95 micrograms/day. The present data demonstrated that the LPIA method enables the urinary FDP to be measured quantitatively with a good sensitivity.