OBJECTIVE To examine saliva- and serum concentrations correlation of estradiol (E2) in women undergoing ovarian hyperstimulation for IVF/ICSI. Saliva measurements could simplify stimulation follow up. A 'home' test for E2 could be useful. METHODS Prospective interventional academic monocentric study at the Centre for Reproductive Medicine of the University Hospital of Ghent, Belgium. Between November 2014 and August 2015 thirty-one patients were included after random selection (inclusion criteria: < 41 years of age, any rank of IVF/ICSI cycle, serum anti- Müllerian hormone concentration ≥ 1 μg/L, treatment completely at the University Hospital.) Measurements took place using immunoassay serum measurements. Estradiol was determined in saliva and serum by LC-MS/MS. At every control, E2 was measured in saliva and serum. Equilibrium analysis on a part of the serum samples took place. Statistic method used is a linear Mixed- Effects model (MIXED) in SPSS. RESULTS Statistical analysis shows a strong linear relation between serum and salivary E2, (R2 of 0.75). E2 in equilibrium dialysis and E2 in serum were also strong correlated (R2 of 0.85). CONCLUSIONS Strong correlation between serum and salivary E2 concentrations was found. Equilibrium dialysis showed good correlation with salivary E2. Saliva can be a good surrogate for free E2 in women undergoing ovarian hyperstimulation. This may create an opportunity to develop a point of care test for measuring E2, in purpose to simplify screening for OHSS risk.