It began in Toronto in 1993 when two dozen people attended a discussion at the American Psychological Association convention entitled "Will Psychology Pay Attention to its Own Radical Critics?"
Members include psychologists and others, academics and practitioners, faculty and students, psychotherapists and patients.
It publishes the online Radical Psychology Journal (published for ten years until its final issue in 2011) and sponsors an active email discussion list.
Challenging psychology's traditional focus on minor reform, members emphasise enhancing human welfare by working for fundamental social change.
They claim that psychology itself has too often oppressed people rather than liberated them and they work to redress this imbalance.