The invention relates to the conditioning of a sample of a liquid for medical analysis. The conditioning device according to the invention, comprises a plurality of calibrated peripheral cells connected to a central receptacle and includes, for each cell, ducts including an air inlet orifice for conveying the sample from the receptacle to said cell to completely fill the cell by centrifuging and an air escape orifice in each cell for the escape of the air contained in said cell closer to the axis of rotation than said inlet orifice and leading into said receptacle, said orifices further being dimensioned so as to retain the liquid contained in each cell after complete filling thereof.