Thyroid abscess was a common condition in the era before antibiotics. In the current medical environment, however, it is a clinical entity that is seldom encountered. We report the case of a unique cause of thyroid abscess, the environmental Gram-negative bacterium Acinetobacter calcoaceticus. Review of the published causes of thyroid abscess since 1980 demonstrated that although Gram-positive bacteria (Staphylococcus and Streptococcus species) remain the most common causes, there has been a marked decrease in the number of cases caused by mycobacteria, Salmonella species, and anaerobes when compared with the early part of the 20th century. Patients infected with the human immunodeficiency virus, however, still develop mycobacterial and fungal thyroid infections with some regularity. Reported modes of management of thyroid abscess vary, but drainage remains an integral component of therapy for resolution of the infection.