Opioid-induced respiratory depression (OIRD) is a potentially fatal complication of treatment with opioids. Little is known about patient- and case-related factors associated with OIRD. One-hundred-and-five available case reports on OIRD in 134 patients (12 years and older) in the perioperative, obstetric or emergency care setting, published since 1980, were retrieved from the literature. The most frequently reported case-related factors were: morphine use, perioperative setting and obstetrics, neuraxial or intravenous administration. The most frequently reported patient-related factors involved were: female gender, sleep-disordered breathing, obesity, renal impairment, pulmonary disease and CYP450 enzyme polymorphisms. While the analysis has limitations, it confirms that OIRD in the acute setting involves complex and interrelated factors and is a significant cause of preventable morbidity and mortality.