Despite the Taser's increasing popularity among police agencies, questions have been raised concerning the weapon's use and effectiveness as well as its potential to cause serious injury or death. This article examines all Taser deployments by the New York City Police Department from 2002 to 2005 (N = 375) and uses two multivariate approaches--logistic regression and chi-square automatic interaction detection--to identify predictors of Taser effectiveness, measured as continued suspect resistance and officer satisfaction. Findings indicate that several factors are associated with reduced effectiveness, including suspect body weight (more than 200 pounds), drug and alcohol use, physical violence, and close distance (3 feet or less) between the officer and the suspect. Although this study represents a preliminary effort at identifying predictors of Taser effectiveness, there are clear training and policy implications for police departments. (Contains 4 tables, 3 figures, and 21 notes.)