This paper reports the results of a field study investigating the effect of user participation and attitude on the success of information system implementation during the system development process. The theoretical framework for this research is based on the organizational change theory, in which the attitude affects the effects of user's participation. User participation and attitude were defined as independent variables and the performance of system implementation as dependent variable. User participation was defined as a direct participation by end users in the process of the new information system development. This was measured by user's participation/non-participation. User attitude refers to user's opinions or feelings before a new system is developed. This was measured by user's favor toward a system. The performance of system implementation was measured by the surrogate variable, the degree of individual satisfaction on developed system. To achieve the objective of this research, a field research method utilizing questionnaires were employed. They were distributed to 221 users present during and/or after system development. Among 185 questionnaires returned, 175 questionnaires were used for analysis. The major findings can be summarized as follows: First, there was no significant effect of user participation on user satisfaction. Second, there was a significant effect of user attitude on user satisfaction. Third, there was no significant interaction effect of user participation and attitude on user satisfaction. It is worth to note that the user's participation did not have any significant effect on the user's satisfaction. It seems the reason for the above result is due to user's involuntary participation. In fact, the user does not have much leverage in the process of system development, which may result in poor performance of user participation. Since user attitude is an important factor in the success of system implementation, however, a method to overcome unfavorable attitude of user should proceed all others.