A lipid‐enveloped virus (Semliki Forest virus: SFV) and a nonenveloped virus (coxsackievirus B4) were treated with neutral lipids known to be present in human milk or able to be generated by lipase activity in human milk. Triglycerides and diglycerides were inactive compared to monoglycerides and free fatty acids which were active against SFV (90% inactivation) at concentrations as low as 0.7 μM. Of the compounds tested monolinolein was the most active against SFV. None of the lipids tested were active against coxsackievirus B4. A synthetic milk (Almiron‐M2), high in unsaturated triglycerides, was inactive against either v