We describe and present a new automatic device to measure the clotting time of a plasma plus reagent mixture by recording the time of transformation : solution to gel. The apparatus is able to perform 50 tests without manual help. Indeed it automatically carries out:--the dispatching of the tested plasma,--the dispatching of the various reagents,--the recording of the clotting time of the sample,--the processing of the data through greater a printer. No contamination is allowed to occur since the tubing and the plates containing the sample are disposable. We obtain accuracy than with the manual method with a coefficient of variation below 3%.