A cluster of infant deaths due to severe metabolic acidosis following immunization was reported in a prosperous farming village in Egypt. Fears that more deaths might occur, and of a deleterious effect on national immunization programs prompted an urgent investigation by national and international partners. The deaths, and other previously unrecognized illness following immunization, were associated with excessive topical application of methanol. Methanol was employed as an anti-pyretic and anti-inflammatory agent following injections. Fear of adverse reactions to vaccine had encouraged increasing use of methanol for these purposes. Local physicians and nurses were unaware of the toxicity of methanol and did not consider it in the differential diagnosis, and thus did not offer appropriate life-saving therapy. The interaction of traditional practices and modern medical interventions can have clinically important consequences, and should be considered when programs are introduced and as they are monitored.