To assess the risk for pelvic inflammatory disease (PID), a practitioner must evaluate the likelihood that a woman has PID or will be exposed to a sexually transmitted disease causing PID. Successful risk assessment depends on accurate information about variables influencing risk of PID. To determine the current state of knowledge about PID risk variables, we examined data in published reports. Data on each risk variable were scrutinized to discern which link(s) in the PID risk chain it affects (acquisition of a sexually transmitted disease, development of PID, or development of PID sequelae) and whether it is a risk marker or a risk factor. Most PID risk variables, particularly sexual behaviors, are associated with acquisition of a sexually transmitted disease, rather than development of PID itself. With the exception of age, demographic and social indicators of risk appear to be risk markers, while contraceptive practices appear more often to be risk factors than risk markers. Additional data are needed for most PID risk variables confidently to categorize them as risk factors. Enough information is available, however, to begin assessing risk for PID, so that appropriate counseling can ensue and timely diagnosis can be made.