Oscillatory nucleation regime in counter flows of vapor and falling droplets is considered. Experiments with such system were made in a diffusion cloud chamber. Oscillation is the results of the feedback between vapor depletion due to condensation on droplets and the value of a supersaturation in nucleation zone. For different pressure of carrier gas (helium) and temperatures, experimental results are presented for dodecane vapor. The new mathematical model of oscillatory nucleation is developed. Three characteristic times defines the duration of the process: nucleation time, time of droplets growth and falling, and, time of diffusion restoration of vapor profile. Experimental data and calculate ones are in good agreement. (c) 2006 Elsevier Ltd. All rights reserved.