How long do I have to hold a job for an employee on medical leave?

If your company is subject to the Family Medical and Leave Act (FMLA) or Americans with Disabilities Act (ADA), you must adhere to their guidelines. Under the FMLA, a worker is entitled to take up to 12 weeks of leave every 12 months for a serious health condition, and to be reinstated to either the same or an equivalent position upon their return. To be eligible for this type of leave, they must have worked for you for at least a year (not necessarily all at once), have worked 1250 hours in the past 12 months, and you must employ 50 employees within a 75 mile radius of the work place (or from the headquarters into which they report if they work from home.) If theirr condition meets the definition of "disability" under the Americans with Disabilities Act (ADA), they may be entitled to more than 12 weeks of medical leave if their request for leave is reasonable and you  cannot show that theirr leave presents an "undue hardship" to your business operations. Whether leave is "reasonable" or constitutes an "undue hardship" will depend upon specific circumstances such as: the length of leave requested, whether you grants leave of that length for other reasons, the nature of their position, etc. That having been said, if  neither the ADA or the FMLA apply, you can terminate the employee not withstanding any employment contract or union agreement to the contrary and so long as the worker has no more available PTO. To be certain of your rights, you should consult diretly with a local empoyment law attorney.