César Milstein was born in Bahia Blanca, Argentina, in 1927. He graduated from University of Buenos Aires and obtained a PhD under Professor Stoppani (Professor of Biochemistry) in the Medical School on kinetic studies with the enzyme aldehyde dehydrogenase. In 1958, funded by the British Council, he joined the Biochemistry Department in Cambridge to work for a PhD under Malcolm Dixon on the mechanism of metal activation of the enzyme phosphoglucomutase. During this work he collaborated with Fred Sanger whose group he joined with a short_term Medical Research Council appointment.

In 1975, Milstein and Köhler described the hybridoma technique for producing monoclonal antibodies. They immortalised antibody producing cells by fusing them with tumour cells. The resulting antibody cell and all its daughter cells produce identical antibody molecules. The method allows unlimited production of monoclonal antibodies with predetermined specificity.

He was elected a Fellow of the Royal Society in 1975 and became a Companion of Honour in 1995.

Cesar Milstein died in March 2002 in Cambridge aged 74.