1 Acute cytogenetic effects expressed as sister-chroma tid exchanges (SCE) in peripheral blood lymphocytes were investigated after in vitro exposure to low vibration regimes (5 - 30 Hz, at 0.1 cm amplitude) for 20 min intervals and compared to non-vibrated control cultures. 2 There was no significant (P<0.05) increase in the range of SCE incidence at any vibration frequency compared to the mean value of control; 6.88 ± 0.11 to 7.97±0.22 versus 6.83±0.86, respectively. 3 When cultures were incubated for 1 h in the presence of 0.5 μg ml-1 mitomycin C (MMC; the positive control) significant elevations in the SCE frequency were observed (19.81 ± 0.67), indicating the sensitivity of the system to in vitro SCE induction. 4 Other cell parameters, such as mitotic index and cell proliferation index were statistically similar in the experimental cultures and the negative control. 5 The observed differences in the investigated end points are considered within those typically found in vitro. This suggests no relation between low frequency vibrations and cytogenetic effects.