Dame Mary Peters described the gender test of her era as "the most degrading experience of my life." Over forty years later, Caster Semenya endured appalling public scrutiny of her eligibility to compete in female competitions.
So why is such an apparently simple question so difficult to answer?
As the IAAF produce new eligibility guidelines for athletes, Chris Ledgard asks if female athletes can ever achieve a truly level playing field.
Physical examination, chromosome testing, androgen testing; whatever tests are applied, how can gender be effectively defined? And whilst wider society can tolerate shades of grey, as long as top-flight competition requires precise definitions of male and female, what are the effects of testing for an athlete's sense of self-worth and identity?
Chris Ledgard asks if gender testing will mean a level playing field for female athletes.