Purpose: The purpose of this study is to empirically test whether it is possible to deliberately develop emotional intelligence (EI) as conceptualized in the Mayer and Salovey model. Design/methodology/approach: This empirical study utilized a sample of 135 fully-employed business students in a treatment/control group research design in which treatment group participants underwent an intensive 11-week EI training program. Additional samples of 270 and 130 fully employed business students were utilized to develop an EI measure appropriate for EI development. Findings: The results indicate that EI can be deliberately developed; the treatment group demonstrated statistically significant overall EI gains and across each EI dimension while the control group did not show any significant pre-/post-test differences. Practical implications: In addition to illustrating EI training best practices a new EI measure is described that is appropriate for leadership development. Research limitations/implications: Research implications are discussed for the role of EI training in leadership development programs and fertile research directions for EI training. Originality/value: Emotional intelligence training has emerged into a popular and lucrative field but empirical evidence on the deliberate development of EI has been substantially more elusive. This study provides an empirical EI training study that overcomes the conceptual and methodological limitations of extant research on the EI development process. (PsycINFO Database Record (c) 2010 APA all rights reserved)