This dataset contains the probability of cancer at different CA125 levels derived from logistic regression analysis and supporting the PLOS Medicine publication: "The diagnostic performance of CA125 for the detection of ovarian and non-ovarian cancer in primary care: a population-based cohort study". The dataset is in Excel format. Sheet A provides the probability of ovarian cancer (with associated 95% confidence intervals) for CA125 levels between 1-1000 U/ml. Sheet B provides the probability of invasive ovarian cancer (with associated 95% confidence intervals) for CA125 levels between 1-1000 U/ml. Sheet C provides the probability of all cancer (with associated 95% confidence intervals) for CA125 levels between 1-1000 U/ml. Sheet D provides the probability of ovarian cancer (with associated 95% confidence intervals) for CA125 levels between 1-1000 U/ml for women aged 30, 40, 50, 60, 70 and 80 years of age.