On 9 February 1965, an outbreak of involuntary behavior — including fainting, hyperventilation, laughing, crying and abdominal pain — began among pupils at a girls' boarding school in the Tanganyika region of East Africa. Within days the episodes spread through the institution and into neighboring schools and communities. Local physicians, visiting psychiatrists and international observers described the phenomenon as an episode of mass psychogenic illness (often historically termed "mass hysteria"). The incident attracted attention for several reasons. First, it involved schoolchildren in a boarding environment, highlighting how closed social settings can facilitate rapid spread of psychogenic symptoms. Second, the behaviors were dramatic and variable, prompting extensive clinical observation. Third, contemporary reports and later scholarly reviews treated the Tanganyika outbreak as among the earliest well-documented examples of contagious mass psychogenic illness in school-age children — a precedent for subsequent case studies in other countries. Medical assessments at the time emphasized the absence of an identifiable infectious, toxic or neurological cause. Investigators noted that symptoms often began after an initial index case and that anxiety, stressors related to boarding-school life, and cultural expectations about illness expression plausibly contributed. Explanations offered by clinicians and social scientists included social contagion via suggestion, heightened communal anxiety amid postcolonial social changes, and the role of authoritative attention reinforcing symptom expression. Historians and psychiatrists have also cautioned against simplistic labels, stressing the complex interplay of social, psychological and cultural factors. Documentation of the outbreak appeared in medical journals, missionary and colonial administrative reports, and contemporary press coverage. These sources reveal both careful clinical detail and interpretive bias of the era: some accounts framed the events in moralizing or exoticizing terms, while others sought to apply emerging psychiatric frameworks. Later reviews by scholars in psychiatry, anthropology and history have reexamined the 1965 Tanganyika events as an instructive early case in the study of mass psychogenic illness among children, useful for understanding similar episodes in diverse settings. The Tanganyika school outbreak influenced how clinicians, school administrators and public-health officials approached similar occurrences. Recommended interventions that emerged from this and subsequent cases emphasized calm, non-suggestive clinical assessment, minimal sensational media exposure, prompt management of environmental stressors, and community engagement to reduce anxiety. The incident also fed academic interest in differentiating psychogenic illness from infectious or toxic etiologies, shaping investigative protocols used in later school-based outbreaks. Uncertainties and disputes remain. Terminology such as "hysteria" reflects historical usage that modern clinicians generally avoid; "mass psychogenic illness" or "functional neurological symptoms" are preferred contemporary terms. Precise causal pathways remain debated: while social contagion is widely accepted as central, the relative contributions of cultural context, gender dynamics in single-sex boarding schools, and broader political or economic stressors in 1960s East Africa continue to be topics of scholarly analysis rather than settled fact. In sum, the February 1965 Tanganyika school outbreak stands as a seminal, well-documented early case of contagious psychogenic illness among schoolchildren. It remains important for historians of medicine and practitioners for the lessons it provides on diagnosis, culturally informed interpretation and non-sensational public-health responses to similar episodes.