Clostridium difficile, a toxin-producing bacterium that causes diarrhea, has been identified as the largest single cause of morbidity and mortality among hospital-acquired infections in many healthcare systems. Most medical research on C. difficile has emphasized individual, or innate, risk factors for infection and has ignored the importance of inter-patient and inter-facility transmission. In this talk, I will discuss the transmission of C. difficile with an emphasis on ongoing work investigating the role of inter-facility patient movement in spreading disease. The measurement of facility connectedness and statistical methods for quantifying the magnitude and timing of transmission will be examined.