The illnesses of two patients with characteristic symptoms of subacute carbon monoxide poisoning were misdiagnosed initially. This resulted in the needless exposure of one patient and two relatives to a toxic environment. The cherry-red color of the skin commonly cited in the literature was absent in both patients. The carbon monoxide poisoning probably contributed to the myocardial infarction and pulmonary emboli seen in these patients. Vague flu-like illnesses should raise the suspicion of carbon monoxide poisoning.