We are developing a fine-grained agent-based model of community associated CA-MRSA for the Chica- go metropolitan area. Time is represented at the hourly level and space is represented at the place and ac- tivity level. The model represents the details of contact and disease transmission and transition for indi- viduals as they go through their daily routines and participate in various activities in various places. The model combines U.S. Census data, samples of individual activity diaries, data from the CA-MRSA litera- ture, clinical data, expert judgments based on clinical experience, and specialized studies. The model pro- vides a detailed picture of general activity patterns of the population, CA-MRSA transmission pathways, and individuals’ behaviors in response to contracting the disease and public health programs. Using tradi- tional epidemic models as a foundation, several modeling challenges (modeling contact, infectivity, be- havior, metrics) are addressed in making the transition to the CA-MRSA ABM, some of which are appli- cable to other diseases that share CA-MRSA characteristics.