Hybridoma technology requires freezing of parental myeloma cells, continuous freezing and thawing of clones and stable hybridoma cells. A modification of the method of two-step freezing is described. The cryoprotective agent (5% dimethyl sulphoxide) is added to the cells at room temperature for 10 min. Cells are then transferred directly to the -25 degrees C bath, held at this temperature for 10 min, and stored directly in liquid nitrogen. Thawing is rapid in a water bath warmed to 60-80 degrees C. Hybridoma cells retain high viability and the production of specific monoclonal antibody after thawing.