Background: Patient satisfaction with antidepressants (ADs) depends on various factors whose individual contributions are incompletely understood. Methods: An online survey was conducted of 1199 Japanese individuals being treated for major depressive disorder. Satisfaction for each AD was quantified using a 5-point scale. The average of all agents was calculated for each subject and defined as the Satisfaction Score (SS). Those on a single AD medication (n=667) were divided into four subgroups based on their medication: fluvoxamine (n = 165), milnacipran (n = 91), paroxetine (n = 196), and tricyclic antidepressant (TCA; n = 103). Among those with higher SS (>= 4.0), their satisfaction reasons were elicited by three multiple-choice responses: efficacy, fewer side effects, and lower dosing frequency. To compare the responses to these three questions among the four subgroups, one-way analysis of variance and post-hoc comparison tests were performed. Logistic regression was done to determine whether these three responses predict higher satisfaction. Results: The number of ADs taken by an individual was negatively correlated with the SS (r= -.074, p =.0 11). SS did not correlate with demographic features. SS was similar among the four subgroups but their satisfaction reasons differed. Predictors of higher SS (SS=5.0 versus 4.0) were reporting "efficacy" and "fewer side effects" as satisfaction reasons. Limitations: Web-based surveys have a selection bias, and diagnoses were based on self-reports. Conclusions: SS waned as the number of ADs increased. Among users of four ADs, SS was similar but their satisfaction reasons differed. Perceived efficacy and fewer side effects predicted higher drug satisfaction. (C) 2007 Elsevier B.V. All rights reserved.