The Developmental Index (DI) has recently been introduced as a composite Rorschach measure of psychological development and maturation, which can be used both with the Comprehensive System (Exner, 2003), and with the recently developed Rorschach Performance Assessment System (Meyer, Viglione, Mihura, Erard, & Erdberg, 2011). As the DI is new, and its validity has not yet been investigated with independent non-U.S. samples, we tested the correlation between DI and age using 3 relatively large samples, 2 of which were from outside the United States (total N = 902). Other Rorschach variables presumably associated with maturation, such as complexity and productivity, were also investigated. As expected, the DI significantly correlated with age, with small variations across the 3 samples. Importantly, the correlation between DI and age remained statistically significant also after controlling for productivity (i.e., the number of responses) and complexity.