Prolonged consumption of excessive amounts of alcohol by itself, as well as possibly leading to a state of alcoholism, has been a long-standing biological/social problem. As a major public health concern, there is an estimated expenditure of about 20% of total health care costs for medical/hospital care related to alcohol-induced illness. In addition, a significant proportion of both men and women who are hospitalized can be classified as alcoholics. This review focuses primarily on one of the many biomedical problems attributed to alcohol abuse—its adverse effects on our immune-defense system. A considerable body of evidence has mounted, over the past several decades, indicating that those who abuse alcohol are more susceptible to certain infectious disorders and are more prone to bacteremia. Such infections tend to be continuous and are often associated with a high rate of mortality. Also, along these lines, various and suitable animal models have been developed to further elucidate what the causes are for the greater frequency and severity of infectious illnesses, and this review deals primarily with those studies linking alcohol abuse to disruption in the normal functioning of the host’s immune surveillance system. Based on the results from both clinical and experimental studies, it would seem that exposure to high levels of alcohol causes decreased humoral and cellular immune responses, thereby seriously limiting our ability to be protected from certain infectious agents.