More employees are using and liking worksite clinics, but their effect on health and costs is hard to quantify.

Researchers at Hewitt Associates Inc., Lincolnshire Ill., have published that conclusion in a summary of results from a survey of 248 large and midsize companies.

The researchers found that 19% offer medical clinics and 11% offer pharmaceutical services to employees in house.

About 25% of the employees who had access to onsite medical clinics used the the onsite clinics, and 50% of the employees who had access to onsite pharmacies used the onsite pharmacies.

At companies that offer clinics, 81% of survey participants said they are satisfied with the clinics, and 95% of the participants with onsite pharmacies said they are satisfied with the onsite pharmacies.

But even when employers offered services such as flu shots, for example, only 30% of employees participated.

Only 24% of the companies with onsite health services programs have a system in place for tracking participation levels or comparing the performance of services vendors, the Hewitt researchers report.