Background and Aims: A definition of gaming disorder (GD) was introduced in ICD-11. The purpose of this study was to develop a short screening test for GD, utilizing a reference GD group. It also sought to estimate the prevalence of GD among individuals, representative of the general young population in Japan. Methods: Two hundred eighty one men and women selected from the general population, aged between 10 and 29 years, and 44 treatment seekers at our center completed a self-reported questionnaire comprising candidate questions for the screening test. The reference group with ICD-11 GD was established, based on face-to-face interviews with behavioral addiction experts, using a diagnostic interview instrument. The questions in the screening test were selected to best differentiate those who had GD from those who did not, and the cutoff value was determined using the Youden index. Results: A nine-item screening test (GAMES test) was developed. The sensitivity and specificity of the test were both 98% and the positive predictive value in the study sample was 91%. The GAMES test comprised two factors, showed high internal consistency and was highly reproducible. The estimated prevalence of GD among the general young population was 7.6% (95% confidence interval; 6.6-8.7%) for males and 2.5% (1.9-3.2%) for females, with a combined prevalence of 5.1% (4.5-5.8%). Discussion and Conclusion: The GAMES test shows high validity and reliability for screening of ICD-11 GD. The estimated prevalence of 5.1% among the general young population was comparable to the pooled estimates of young people globall.  Kulcsszavak: ICD-11, gaming disorder, internet gaming disorder, screening test, validity, prevalence