Two combined mechanical and enzymatic disaggregation techniques and a simple mechanical disaggregation procedure were compared. The combined procedures involved a mechanical comminution of the tumour tissue followed by incubation in trypsin. In one method, the tissue was subjected to long-term trypsinization at 4 degrees C, and in the other procedure, repeated short-term trypsinization at 37 degrees C was applied. The results were compared in terms of the yield of viable cells, plating efficiency, the ability to produce tumours in nude mice, and DNA distribution as measured by flow cytometry. The combined techniques provided reproducible cell yields of 2-10 X 10(7) viable cells g-1 of tissue, whereas only a small number of tumour cells was produced by the mechanical method. DNA analysis demonstrated that only the long-term trypsinization procedure resulted in a representative cell yield from all the tumours tested.