We report here the application of the LAL Test to a chromogenic substrate to detect endotoxins in Human Blood Products. In order to reduce the cost, we used a microplate procedure with the Multiskan Reader. Quantitative results in the range of 0,01 to 0,1 ng/ml allowed for a good correlation with the Rabbit Pyrogen test. For 20% albumins and 4% albumins, the mean endotoxins levels of non pyrogenic lots were 0,38 +/- 0,18 and 0,09 +/- 0,03 ng/ml. All the lots which passed the Rabbit Pyrogen test had endotoxins levels lower than 1 ng/ml and 0,2 ng/ml, respectively. We can use this test for other plasma derivatives; Gammaglobulines and PPSB are easily tested. Dried Concentrated Antihemophilic Factor and Dried plasma contain citrate which inhibits the reaction. Dilution and Addition of Calcium Chloride overcome this inhibition. For dried plasma, we should destroy plasma inhibitors by heating at 75 degrees C. This sensitive and reproductible in vitro assay improves the control of pyrogenecity in Human Blood Products.