The concentrations of radon decay products 214Pb(RaB) and 214Bi(RaC) and thoron daughter 212Pb(ThB) have been measured in rainfall at Bombay. The presence of short-lived 218Po(RaA) is indicated in a few samples. The levels of 214 Pb varied from 300 to 7000 pCi (11-260 Bq) per liter, while the activity ratios of 214Bi/214Pb are in the range of 0.5-1.5. From these values of the ratios a cloud drop lifetime, from nucleation to deposition, of 20--60 min is estimated. The concentrations of 212Pb varied from 2 to 30 pCi (0.075-1.1 Bq) per liter. The levels of radon and thoron daughter products are lower in Bombay summer rainfall compared with other areas due to their reduced concentrations in the maritime monsoon winds. Approximate estimates of scavenging ratios based on the surface air concentrations are 85¿65 (1 standard deviation) and 30¿20 (1 standard deviation) for radon and thoron daughters, respectively.