In the northern region of Brazil, cervical cancer is the most important cause of cancer-related deaths among women. There is considerable likelihood, however, that official incidence and mortality figures are greatly underestimated. The aim of this study was to estimate the repercussions from improvement in cervical cancer screening programs on the incidence of pre-invasive and invasive cervical lesions in a municipality in this region. This was a quasi-experimental study that assessed process dimensions relevant to the program objectives. The study comprised a sample of 2,226 women seen at primary healthcare units in Cruzeiro do Sul, a small city in the Brazilian Amazon region, from April 2003 to July 2004. Women were recruited through local radio advertisements and by oral communication from the investigators. The women answered a structured questionnaire and underwent pelvic examination, which included Papanicolaou (Pap) smears and naked-eye inspection of the cervix after applying diluted acetic acid. Women with positive Pap smears or abnormal gynecological examination were referred for colposcopy and possible biopsy, diathermic large loop excision of the transformation zone or conization. The results obtained were compared with historical official data retrieved from the Brazilian Ministry of Health's database. Intervention resulted in a 40% increase in positive Pap smears and detection of cancer was nine times higher than had been observed in routine screening. Detection of pre-invasive and invasive cervical lesions in the intervention group was remarkably higher than among women seen during routine screening.12542-