The Job Characteristics Model proposed by Hackman and his associates postulates that positive personal and work outcomes are derived from five core job dimensions: skill variety, task identity, task significance, autonomy, and feedback from the job. The effects of the number of workers (work group size) and the number of tasks (task size) on perceptions of job characteristics were investigated using a simulated assembly line job. Subjects (N=40) observed videotaped workers performing a job in four combinations of work group size and task size, and rated the respective jobs on dimensions taken from the Job Characteristics Model, using the Job Rating Form. Results indicated that jobs performed by smaller work groups were perceived as significantly higher on the job dimensions of skill variety, task identity, feedback from the job, and autonomy, and had greater potential for employee motivation. Significant main effects were also found for task size on the dimensions of skill variety and feedback from the job; jobs with larger tasks were seen as having greater motivating potential for the employees. The findings suggest that work group size appears to have a more potent effect than task size. (Author/NRB)