I ordered a large based on reviewers comments.  I'm glad I did because it definitely runs small.  I'm 5'3" 140 lbs and a 34D and the fit is a deep V neck (shows a lot of cleavage), somewhat loose fitting, and very long.  I like the look and feel of the shirt very much and it did shrink a bit upon first wash.  I will probably order again but in a medium.