Item Response Theory (IRT) models were applied to investigate the psychometric properties of the Arthur and Day's Advanced Progressive Matrices-Short Form (APM-SF; 1994) [Arthur and Day (1994). "Development of a short form for the Raven Advanced Progressive Matrices test." "Educational and Psychological Measurement, 54," 395-403] in order to test if the scale is a reliable and valid tool to assess general fluid ability in a short time frame. The APM-SF was administered to 2264 high-school and university students. Once attested the one-factor structure of the scale, unidimensional IRT analyses for dichotomous data were applied to investigate the increases in item difficulty levels, Test Information Function, and Differential Item Functioning across age, gender, and country (comparing Italian and British respondents). Additionally, validity measures were reported. Findings attest that the Arthur and Day's APM-SF is a sound instrument for assessing fluid ability within a short time frame. (Contains 3 tables and 1 figure.)