We aimed to develop and validate a clinical nomogram predicting bladder outlet obstruction (BOO) solely using routine clinical parameters in men with refractory nonneurogenic lower urinary tract symptoms (LUTS).A total of 750 eligible patients ＞50 years of age who had previously not responded (International Prostate Symptom Score [IPSS] improvement ＜4 points) to at least three different kinds of LUTS medications (including α-blocker) for the last 6 months were evaluated as subcohorts for nomogram development (n =570) and for split-sample validation (n =180).BOO was defined as Abrams-Griffiths number ＞40,or 20-39.9 with a slope of linear passive urethral resistance ratio ＞2 cmH2O ml-1 s-1.A stepwise multivariable logistic regression analysis was conducted to determine the predictors of BOO,and β-coefficients of the final model were selected to create a clinical nomogram.The final multivariable logistic regression model showed that age,IPSS,maximum urinary flow rate,postvoid residual volume,total prostate volume,and transitional zone index were significant for predicting BOO;these candidates were used to develop the final nomogram.The discrimination performance of the nomogram was 88.3％ (95％ Cl:82.7％-93.0％,P ＜ 0.001),and the nomogram was reasonably well-fitted to the ideal line of the calibration plot.Independent split-sample validation revealed 80.9％ (95％ CI:75.5％-84.4％,P ＜ 0.001) accuracy.The proposed BOO nomogram based solely on routine clinical parameters was accurate and validated properly.This nomogram may be useful in determining further treatment,primarily focused on prostatic surgery for BOO,without impeding the detection of possible BOO in men with LUTS that is refractory to empirical medications.