The survival rate of cells of the genera Arthrobacter, Pseudomonas, Mycobacterium, Escherichia, Micrococcus and Saccharomyces when counted immediately after fast or slow drying (20 minutes and 24 hours, respectively) was rather similar. However, after prolonged periods of dry storage, the number of viable cells after slow drying was much higher as compared with the rapidly dried cells. Investigations with Escherichia coli demonstrated this phenomenon only when more than about 8 mg of water per 10(8) cells was available on a filter paper disc. In order to obtain optimum resistance to water loss the dessication period of 0.025 ml of suspension of E. coli must be longer than 13 hours.