Twenty collections of peripheral blood stem cells were performed in 3 patients (2 NHL, 1 AML) using the Haemonetics V50S discontinuous flow blood cell separator. A modified lymphocyte collection protocol (Nebraska Surge) was used in all instances. Leukapheresis were performed after 1 or 2 courses of chemotherapy and started when peripheral blood leukocytes count reached 1 x 10e9/l and platelets count 80 x 10e9/l. A mean blood volume of 5.9 +/- 0.6 litres was processed per procedure and the mean yields for mononuclear cells, nucleated cells and CFU-GM were respectively 5.4 +/- 1.4 x 10e9, 4.9 +/- 1.6 x 10e9 and 128.5 +/- 182.3 x 10e4 per procedure. Haemonetics V50S had showed a mean collection efficiency for mononuclear cells of 67.5 +/- 5.0% per procedure. Results obtained are not significantly different from the ones obtained with an automated continuous flow separator even if extracorporeal circulation is consistently high in patients with a low hematocrit when the 250 ml Latham Bowl is used.