The purposes of this research were to investigate influence of job-relevant and job-irrelevant factors , and to investigate interactions between job-relevant and job-irrelevant factors on decisions concerning middle-level executive selection. A 2x2x2x2 factorial design was used for this study. Independent variables were job-relevant factors (academic qualification and work experience) and job-irrelevant factors (sex and physical attractiveness). Dependent variables were favorability rating of applicant, hire recommendation and starting salary recommendation. The sample was 80 personnel managers or others who had authority in selection from business organizations in Chiang Mai and Lamphun. The research instruments consisted of a demographical data questionnaire, a job description, bogus application blanks and applicant evaluation forms. The statistics for data analyses were descriptive statistics, hierarchical multiple regression analysis and analysis of covariance. The research found that: (1) There were influence of job-relevant and job-irrelevant factors on favorability rating of applicant and hire recommendation. The most influential factor on favorability rating of applicant was academic qualification, the next were work experience, physical attractiveness and sex, respectively. The most influential factor on hire recommendation was work experience, the next were academic qualification, physical attractiveness and sex, respectively. (2) There were interactions between academic qualification and work experience, and between academic qualification and physical attractiveness that could predict favorability rating of applicant. In addition there were interactions between sex and physical attractiveness, and among academic qualification, work experience, physical attractiveness that could predict hire recommendation. (3) Male applicants received a higher starting salary than female applicants after controlling for other independent variables. (4) High-physically attractive applicants received a higher starting salary than low-physically attractive applicants after controlling for other independent variables.