A case-control study was performed in Kanagawa Prefecture, Japan, which introduced lung cancer screening, by family physicians, to determine if this program was effective. The subjects were persons who died from lung cancer, restricted to those between 40 and 74 years old at death, and National Health Insurance (NHI) holders. A total of 193 lung cancer deaths meeting the criteria were selected for the case group. Three controls for each case were selected at random from living NHI holders matched by residence, gender and year of birth (+1 year). Smoking adjusted odds ratios were calculated using a multiple logistic regression model. The odds ratios of dying from lung cancer for screening participants within 12 months compared with non-participants was 0.535 which was statistically significant (95% CI, 0.337-0.850). The odds ratio in the 12-24-month period before diagnosis was 0.638 (0.302-0.967), which was also significant. The results demonstrated that screening for lung cancer by family physicians can reduce the lung cancer mortality, and that a clinic-based screening program by family physicians is effective.