The key issue is WHY were you terminated. While you cannot generally be terminated for being disabled, or for using some protected leave (e.g. FMLA leave) or other protected right, being out on disability does not protect you from termination for unrelated reasons. Thus, someone on STD could lose their job due to a restructuring or downsizing; or because of performance issues or violations of company policy. What sometimes happens though is that real reason for termination is using leave or being disabled and the stated reason is just a pretext or excuse. If you think that is the case, then you should consult with an employment attorney who can evaluate your situation in detail. Good luck.