Biological effects induced by ultrasound were frequently reported for continuous wave (cw) mode. Thresholds for the onset of bioeffects of pulsed ultrasound, starting from diagnostic conditions, have not yet been defined by standardized in vitro models. We therefore investigated the effects of pulsed ultrasound on cultured cells using diagnostic ultrasound devices, a selfmade transducer and a sonochemical laboratory reactor tunable from pulsed diagnostic conditions to cw ultrasound. Additionally, we determined physical parameters of the ultrasonic field by different types of hydrophones. Sonochemical reactions and the effects induced by the ultrasonic fields in cultured cells indicated a threshold for bioeffects.