Mimi, I would say it depends on how you want it to fit. The small is snug on me, but I like it that way to tuck into pants and wear under a fitted wool suit. If you aren't sure, you could order both sizes and send one back, I've been doing a lot of that lately. You can see how I look since I lost weight here:
http://forums.teamestrogen.com/showp...5&postcount=30
In the after pic I am wearing shebeest tights and top in small. I am between a small and medium depending on the item. Sometimes I size up to M for length, but the small ribbie has good length both overall and in the arms.
Sure Lisa, we can be Mulberry Ribbie sisters tomorrow!!