[FuzzieAlum]

Therein lies the question ... how do you define biggest?

Most undergrad chapters?
Most total chapters (including grad or alum)?
Most people initiated?
Most living people initiated?
Most currently active collegians?
Most chapters installed (even if not active)?

You're going to come up with different answers ... From what I've seen on this thread, Beta Sigma Phi has the most chapters of any women's fraternal org. Most undergrad chapters, an NPHC group will win. You could narrow it down, say, "only collegiate fraternal orgs," or "only NPC orgs." Now clearly Chi O is the biggest NPC org, but I think it's a stretch to call them the biggest women's fraternal org, looking at the numbers of Beta and the NPHC groups.