The purpose of this research is to examine the relationship between budgetary slack and factors influencing the creation of budgetary slack. This study is a survey research using questionnaire as an instrument to collect data. The sample includes 172 manufacturing companies listed on the Stock Exchange of Thailand using sales managers as respondents. There are 104 usable questionnaires received, representing 60.47 percent response rate. The variables include profiles of respondents, budgetary slack and factors influencing the creation of budgetary slack including information asymmetry, budget emphasis, budget participation, influencing power of managers, positive budgetary feedback, negative budgetary feedback, intrinsic rewards system, and extrinsic rewards system. The results show that most listed companies have moderate level budgetary slack. The results using analysis of variances indicate that years of work experience in companies of sales manager effect all of the eight factors influencing the creation of budgetary slack. Furthermore, the results using multiple regression analysis indicate that 5 out of 8 factors including budget emphasis, budget participation, influencing power of managers, negative budgetary feedback, and extrinsic rewards system are positively related to budgetary slack at the significant level of 0.05. Therefore, in the budgeting process, these factors should be controlled in order to reduce budgetary slack.