When incubated in natural (nonsterilized) soil, P. aeruginosa died initially at a rate which approximated the rate for starvation of a pure culture in buffer. Predation by other soil microbes or phage did not appear to be involved, and pycocyanin either was not produced or was ineffective. The initial rate of death was followed by a 2nd, considerably slower rate. Cells initially added in low numbers to soil also underwent biphasic death as above. Slow drying of the soil caused a period of rapid death of P. aeruginosa, but this then slowed to give residual numbers and a death rate similar to the 2nd death rate noted for soil not allowed to dry. The cells in the dry soil had not changed genetically to a desiccation-resistant form. P. aeruginosa died out completely in a relatively short time when the soil was first quickly dried to a water content similar to that obtained initially through slow drying, and then further allowed to dry slowly. There is apparently a dormant form, in some ways resembling a cyst, for P. aeruginosa in soil.