I had a hard time seeing much of a difference between S and XS apart from arm length.These shirts have so much stretch that you could probably size down, stay true to size, or size up and they would all be very similar fits. I could feel a little difference when putting them on and although the arms on both of them were too long for me, the XS arms will still shorter in comparison. I'd say if wearing under scrubs, you can size down. If wearing on it's own, stay true to size.It's very soft and comfortable, and the material is a high quality one. I'm debating whether to keep due to the incredibly long arms.
Rating: [4 of 5 Stars!]