Thanks to all who replied to my query. The quick responses were very helpful as I could not reach local colleagues who have copies of standard references. Thanks to all of you, I was able to give this mother accurate information showing that bactrim is compatible with BF. You made her Christmas (and her toddler's) a lot happier. Hopefully she will be able to educate her doctor so that future moms won't have this dilemma. Thanks again. Julia Griffith, LLL in Toledo, Ohio