The authors adapted to the cerebrospinal fluid (CSF) the staining technic developed by Anguiano and Ancira to perform differential leucocyte counts in the counting chamber. The formula they used is the following: methyl alcohol 1 ml, destilled water 2 ml. To this mixture are added: 6 drops of Leishman stain filtered in Whatman paper number 42; toluidine blue 0.25% aqueous solution (filtered in the same manner), 1 drop; acetate buffer 0.1 M, pH 5.4, 1 drop. The technic varies according to the intensity of pleocytosis. If the CSF is turbid or contains more than 100 cells per c.m. 1 drop is dripped in the botton of a 10X75 test tube and then 2 drops of the staining fluid are added; the mixture is then snaked; after one or two minutes 1 drop is placed in the Fuchs-Rosenthal counting chamber. If the number of total cells is less than 100 per c.m. (Table 1), different CSF volumes are centrifuged at the rate of 2000r.p.m., during 6 minutes; the supernatant fluid is poured off and the sedimented cells are suspended in 2 drops of the staining fluid. The morphology of the cells as they appear after they are stained by the supravital staining technic (SVST) is described and illustrated in photomicrographies. By using the technic described by Moraes-Rêgo and Fernandes the authors enumerated the first 200 cells encountered in each of 10 smears of the same samples of CSF containing 250 cells per c.m., and calculated the standard desviation (SD) for each (Table 2). In another experiment they counted 200 cells in 10 samples of CSF with different levels of pleocytosis, by both technics. By applying the SD to the cell counts in stained smears they determined the accetable superior and inferior limits for each count (Table 3). There one verifies that the corresponding counting by SVST fell between the maximum and minimum accetable values. With the experience acquired in 5 years of intensive countings by the SVST the authors consider this technic the most adequate for differential counts of leucocytes in the CSF.