Under the guidance of an experienced and qualified teacher, yoga is generally safe.   However there are many different styles of yoga—including some that are quite challenging.  For example, Ashtanga yoga is a very athletic style, while Kripalu yoga tends to be gentler. If you attend a large group yoga class that is too demanding for your specific level of conditioning, you may risk injury.   It’s very important to be sure you’re in a class that is appropriate for you and that you inform the instructor of any health concerns.  If you have a specific medical condition, consult your health care provider for guidance.   Also, be aware that some classes called yoga, are actually “yoga-flavored” exercise classes taught by instructors with minimal yoga training.