6072 Background: Since 1980s, 18FDG-PET imaging has been used as a modality to improve cancer patient management. Although 18FDG-PET scan is potentially useful in early detection of disease recurrence after primary treatment in cancer patients, its effectiveness in cancer screening is still unclear. Nevertheless, in Japan, very recently, asymptomatic individuals consult PET clinics for cancer screening. The total annual number of them has exceeded 5000 at the Nishidai clinic, Tokyo, Japan. Methods: From Aug 1, 2002 to Jul 31, 2003, 5816 consecutive voluntary subjects were examined with whole-body 18FDG-PET scan (Posicam-HZL, Positron Corporation) at the Nishidai clinic. We retrospectively analyzed the data of subject characteristics, and the result of PET scan screening combined with other modalities. Results: Out of 5816 subjects, 4909 asymptomatic healthy subjects without cancer history (2496 men and 2413 women) were analyzed. The mean age was 54.7 (SD=10.8) yrs. The subjects diagnosed positive by PET were 568 (11.6%), those who were suspected of the possibility of cancer were 332 (6.8%), and the subjects diagnosed as cancer proven by histology were 39 (0.8%), including 16 thyroid (all papillary carcinoma), 9 colorectal (all adenocarcinoma; stage 0/I/II/IIIA/IV:1/2/2/2/1 and 1 multiple colon cancer), 5 lung (all NSCLC; stage IA/IIB/IIIA:3/1/1), 5 breast (1 DCIS, 1 invasive ductal, 3 cytologically proven; Stage IIA/IIB:1/1 and not reported in 3), 2 prostate (both adenocarcinoma; Jewett stage C and D), and 1 renal cell (stage I) and 1 double cancers (ovarian and endometrial). False negative diagnosis reported was 14(0.3%), including 4 thyroid, 4 lung, 3 prostate, 3 renal cell, 1 breast and 1 bladder cancers. Positive predictive value of cancer screening in the PET center was 11.7% (95%CI 9.9%–13.5%) in this voluntary population. Conclusions: Overall cancer prevalence was suggested more than 0.8% in this voluntary population at the PET center, and this is approximately 3 fold of the annual cancer mortality rate in Japan. Although at present PET screening has some limitations: false negative and false positive risks, this result warrants further prospective cohort studies. No significant financial relationships to disclose.