On 15 April 1966 a cluster of acute behavioral and somatic symptoms began among students at a secondary school in the northeastern region of then–Tanganyika (shortly before the country became Tanzania). The first cases involved fainting, crying, headaches and abdominal pain. Within hours and days similar symptoms spread through the all-female student population, prompting school closures and attention from local health authorities. Clinical teams who investigated the outbreak documented rapid onset and recovery for most sufferers, absence of objective laboratory or microbiological evidence of infection, and a pattern of spread consistent with social contagion: symptoms appeared first among close contacts and then more broadly among peers. Investigators noted prominent features such as hyperventilation, fainting, and dissociative or trance-like behavior. The episode attracted attention in regional public health records and later appeared in reviews of mass psychogenic illness because it illustrated key diagnostic features: sudden onset, lack of identifiable organic cause, predominance among a cohesive social group, and resolution without specific medical treatment. Historical context matters. Tanganyika in the mid-1960s was newly independent (1961) and undergoing social change, including expanding formal education for girls. School environments, close living conditions, and heightened social stresses have been associated in the literature with outbreaks of mass psychogenic illness. Investigators at the time and later commentators emphasized psychosocial stressors, local beliefs about health, and the visibility of symptoms in crowded institutional settings as contributory factors. While contemporary case reports and public health reviews treat the Tanganyika 1966 episode as a clear example of mass psychogenic illness, some details remain limited in public records. Precise counts of affected students, detailed timelines for each case, and comprehensive contemporaneous laboratory testing are not consistently available in the accessible literature. Where uncertainties exist, historians and clinicians caution against overinterpreting single reports and encourage comparing multiple documented outbreaks to understand common mechanisms. The 1966 Tanganyika school outbreak influenced later thinking about how to recognize and manage similar events. Public health guidance that emerged from subsequent experience emphasizes rapid epidemiologic assessment to exclude toxic or infectious causes, clear communication to reduce anxiety and rumor, and minimizing unnecessary medical interventions. In school settings, prompt reassurance, separation of symptomatic and anxious individuals when appropriate, and involvement of community leaders and parents have been recommended to restore confidence and prevent further spread of symptoms. Because mass psychogenic illness sits at the intersection of medicine, psychology and culture, historical episodes like the 1966 outbreak are studied both for their clinical features and for what they reveal about community responses to stress. They also underscore the importance of careful, culturally sensitive investigation and reporting: labeling an event as psychogenic requires rigorous exclusion of other causes and attention to the social dynamics that produce and sustain symptoms. In summary, the April 15, 1966 school outbreak in Tanganyika is frequently cited in public health literature as an early documented case of mass psychogenic illness. It remains a reference point for clinicians and public health practitioners seeking to distinguish between infectious or toxic outbreaks and illness arising from social and psychological processes within a group setting.