In May 1927, an outbreak of methanol poisoning emerged after a diphtheria antitoxin preparation used in several communities was found to be contaminated. The antitoxin, intended to treat and prevent diphtheria complications, had been prepared using alcohol that was later identified as containing toxic methyl alcohol (wood alcohol). Patients who received the contaminated antitoxin developed symptoms consistent with methanol poisoning, including visual disturbance, abdominal pain, dizziness, and in some cases permanent blindness or death. The incident occurred during a period when antitoxins and other biologicals were often produced and transported under variable quality controls. Medical and public health authorities at the time investigated clusters of unexpected illnesses following antitoxin administration and linked them to contaminated lots. Contemporary reports and later historical reviews indicate that the contamination likely stemmed from the alcohol used during production or preservation of the antitoxin rather than from the diphtheria toxin or serum itself. Investigators sought to identify the source and chain of custody of the alcohol, examine manufacturing practices, and determine how methyl alcohol entered the supply. The tragedy highlighted weaknesses in oversight, manufacturing standards, and testing for purity in pharmaceutical and biological preparations of the era. It contributed to growing awareness of the need for stricter controls, standardized assays, and clearer regulations governing the production and labeling of medical substances. Documentation from the period is not always comprehensive, and some details about the number of affected patients, the exact locations, and the specific manufacturing entities involved vary among sources. What is clear from contemporaneous public health communications and later historical assessments is that the event stands as one of the earlier documented instances in which contaminated alcohol in a medical product led to a cluster of poisonings. The broader context includes the public health challenges of the 1920s: infectious disease control relied on antitoxins and serums produced in multiple facilities with differing practices, and regulatory frameworks were still evolving after reform movements earlier in the century. Incidents such as the 1927 antitoxin contamination fed into ongoing reforms aimed at improving pharmaceutical manufacturing standards, laboratory testing, and government oversight to prevent similar tragedies. While this 1927 event is sometimes grouped with other methanol poisoning episodes tied to beverage adulteration or industrial alcohol diversion, it is distinct in that it involved a medical product. The case underscores how methanol — chemically similar to ethanol but far more toxic — became a recurring hazard when substitution, contamination, or mislabeling occurred in any context where alcohols were used. Because some primary records are fragmented and contemporary reporting can be inconsistent, historians and public health scholars exercise caution when citing precise casualty counts or attributing responsibility to specific firms without corroborating archival evidence. Nonetheless, the incident remains an important early example of mass toxic exposure linked to contaminated medical supplies and helped spur improvements in pharmaceutical safety and regulation.