The Quebec Neuroblastoma Screening Project was initiated to assess the clinical and biological aspects of screening infants for the presence of neuroblastoma in North America. All children born in the province of Quebec from May 1, 1989 to April 30, 1994 are eligible for participation. This report provides results from 22 months' accrual of infants who were screened using urine-saturated filter paper for determination of the catecholamine metabolites vanillylmandelic acid (VMA) and homovanillic acid (HVA). More than 157,000 infants have been screened to date at 3 weeks of age, representing 92% of the entire birth population of Quebec. Over 98,000 infants have been screened a second time at 6 months of age, which made up 76% of the Quebec birth cohort. After a two-stage initial screening, 340 (0.13%) infants (182 at 3 weeks and 158 at 6 months) required second laboratory examinations because of elevated levels of urinary VMA, HVA, or both. Twenty infants from the 3-week screening (0.01%) and nine from the 6-month screening (0.01%) were subsequently referred to one of four Quebec pediatric oncology centers for neuroblastoma evaluation. Seven of 20 children from the 3-week screening and two of nine children from the 6-month screening have been identified as having neuroblastoma. During the same period, 14 additional children in the birth cohort were diagnosed clinically with neuroblastoma; eight were diagnosied prior to screening at 3 weeks of age, three children had negative results at 3 weeks of age, two had negative results at 3 weeks and at 6 months of age, and one had never been screened. Various biological parameters on patients detected thus far by screening, including tumor DNA ploidy, N-myc oncogene amplification, and histologic classification, as well as serum levels of neuron-specific enolase and ferritin plus urinary catecholamine metabolites, suggest the presence of neuroblastomas with a favorable prognosis. The only patient in the Quebec cohort who had progressive neuroblastoma and died, having never been screened, demonstrated biologic markers indicating an unfavorable prognosis. Results of this preliminary analysis suggest that neuroblastoma in children in North America can be detected by urinary screening with very high specificity and a high predictive value. However, for the Quebec Neuroblastoma Screening Project, it is still far too early to determine whether preclinical detection will lead to reduced population-based mortality for neuroblastoma.