More than 90 percent of the employers surveyed by Dr. Jeffrey Harris of the University of Washington School of Public Health and Community Medicine said the potential savings and less absenteeism were important.

Physical exams, immunizations and cancer and cholesterol screenings were among the preventive services most often covered by employers.

"Employers seek financial return from their offerings of clinical preventive services to employees, but they are least likely to offer the services most likely to provide this return," Harris said.

Twenty percent of the programs included services to help employees quit smoking, tackle alcohol abuse, eat better or get more exercise. Flu shots, another relatively low-cost service with a high potential financial return, were also covered by few employers, said Harris.

The findings were reported in the American Journal of Health Promotion.