A new fast, and easy assay based on the "cell squash" method for analysis of a large number of tobacco cell cultures which produces phosphohydrolytic enzymes is described. The time course of growth and changes in the amount of the secreted phosphohydrolytic enzymes, such as acid and alkaline phosphomonoesterases or acid and alkaline specific or nonspecific phosphodiesterases (exonucleases), in Nicotiana tabacum 1507, 1508, and 1509 cell cultures selected by this method were studied. The highest amounts of phosphohydrolytic enzymes were measured in the culture medium of N. tabacum 1507 at 2.8 mu kat ml(-1) for alkaline phosphodiesterase and 2.5 mu kat ml(-1) for the acid enzymes. The amount of 5’-phosphodiesterase and 3’-phosphodiesterase produced was 0.93 mu kat ml(-1) and 1.1 mu kat ml(-1), respectively. The culture line N. tabacum 1508 which was derived from the N. tabacum 1507 that secreted double the amount of extracellular alkaline phosphohydrolases produced the same amount of 5’-phosphodiesterase as N. tabacum 1507.