Objective: To analyse the usefulness of plasma anti-mullerian hormone (AMH) measurement as a tool for assessing ovarian reserve in a general infertility population. Materials and methods: Plasma AMH levels were analysed in 238 women aged 18-46 years during day 3-5 of their menstrual cycle. All 238 patients had follicle stimulating hormone (FSH) levels less than 10 i.u./L, suggesting normal ovarian reserve on traditional FSH criteria. Eighty-seven patients gave their consent to correlate their AMH levels with IVF oocyte retrieval outcome. Patients producing >= 8 oocytes were classified as having normal ovarian reserve, while those producing ! 4 oocytes were classified as having poor ovarian reserve. Results: Plasma AMH levels remained relatively static (20-25 pmol/L) from 18 to 29 years of age. By 30 years of age, plasma AMH levels start to drop rapidly, reaching only 10 pmol/L by 37 years. Despite this 50% fall in AMH levels between 29 and 37 years of age, minimal changes in FSH levels were observed. Using a cut off value of 8.1 pmol/L, plasma AMH assessment could predict poor ovarian reserve on a subsequent IVF cycle with a sensitivity of 80% and a specificity of 85%. Conclusions: Plasma AMH assessments are superior to FSH in identifying women with reduced ovarian reserve. Anti-mullerian hormone assessment should be considered as a useful adjunct to FSH/oestradiol levels and antral follicle count when estimating ovarian reserve.