I believe there are 13-14 NPC groups and new member classes are 30-40. It is a fully structured recruitment with a Welcome Round (Open House), Welcome Back Round, Philanthropy Round, and Preference.
Their Greek Life site is very detailed and can probably answer a lot of questions -
http://www.uiowa.edu/~greek/recruitment/greek_life.html
Here's a good previous discussion -
http://www.greekchat.com/gcforums/sh...niversity+iowa
Have fun!