- 47th Boston Marathon won by Gerard Cote of Canada in 2:28:25.8; his 2nd of 4 wins in the event
- Bicycle Day - Swiss chemist Dr. Albert Hofmann deliberately takes LSD for the first time.
Jews refuse to surrender the Warsaw Ghetto to SS officer Jürgen Stroop, who then orders its destruction, beginning the Warsaw Ghetto Uprising
- Alexander Schmorell, German resistance fighter, beheaded
- Gustave Doret, Swiss composer, dies at 76
- Willy Graf, German resistance fighter, beheaded