Many men who wish to start a family but lack sperm in their semen undergo surgical exploration of the testes in the hope of extracting sperm at source. However, there are currently no tests that can accurately predict whether sperm will be found. We performed proton spectroscopy at 3T in the testes of eight infertile patients and nine controls. Choline concentrations were significantly lower in patients (mean 1.4mM, range 0.8 – 1.9mM) than controls (mean 4.1mM, range 3.0 – 5.1mM), p<0.0001. This suggests that choline, which is a marker of membrane synthesis and cell proliferation, may be useful for detecting spermatogenesis noninvasively.