Relative risk (RR) of false positive recall in current versus never-users of hormone replacement therapy (HRT), by preparation currently used. *Stratified by screening centre, age, previous screening, body mass index and previous breast operation. Relative risks are shown as black squares with areas inversely proportional to the variance of the log relative risk, indicating the amount of statistical information available for that particular estimate. The corresponding confidence intervals (CI) are shown as horizontal lines. An arrow is used where the upper confidence limit exceeds the scale of the figure. The diamond represents the overall relative risk and 95% CI of false positive recall in current versus never-users of HRT.