OBJECTIVE This paper presents an analysis of lag phase phenomena in Saccharomyces cerevisiae growth as a function of ultrasonic irradiation. RESULTS Pulse irradiation treatments were performed by a 20 kHz ultrasonic transducer with different durations and energies. Data obtained from experiments were then employed to estimate growth parameters by specific transfer function. The significance of the different lag times in response to ultrasonic irradiation was analysed. The results showed that the yeast growth in lag phase responded to the irradiated ultrasonic of 20 min more than the 10 min. The ultrasonic energies between 330 and 360 W s m(-3) could decrease lag time up to 1 h compared to the sample without ultrasonic irradiation. Conversely, the treatments with energies higher than 850 W s m(-3) were able to extend the lag time and decrease the yeast growth. CONCLUSIONS The lag durations of S. cerevisiae were changed significantly by different ultrasonic irradiations, energies and durations. In particular, sufficient irradiation energies reduced the lag time, resulting in accelerated yeast growth. In contrast, high energy could inactivate growth by increasing the lag time. CONCLUSIONS This work provides an alternative technique to either accelerate or inactivate the S.cerevisiae lag phase. The approach can be developed in experiment designed to control the yeast growth by ultrasonic irradiation as assistance in the environments.