We examined the statistical relationships between dysbacteriosis and (pre)neoplasia related to age and ethnicity from the cervical screening of almost half a million smears. Data from 445,080 smears were coded according to KOPAC (the Dutch national cervical smear coding system) with nine grades. Prevalence per 100,000 smears and relative risks (RR) were calculated for dysbacteriosis and for squamous abnormalities. Patients were stratified by their probable country of origin. Dutch women had an RR of 0.92 for dysbacteriosis. Surinamese women had the highest RR for dysbacteriosis (RR = 2.36) and Moroccan women had the lowest (RR 1.00). The same trends were seen for the risks of squamous abnormalities. The data for Turkish women follow the patterns of those for Surinamese women. The RR of dysbacteriosis is highest at 50 yr (1.28) and lowest at 35 yr (0.86). When dysbacteriotic and non-dysbacteriotic smears were compared, dysbacteriosis was observed more frequently in smears with squamous abnormalities (4.1% vs. 2.2%). Dysbacteriosis may warrant more intensive cytological surveillance and changes in lifestyle.