Objective. To externally validate the M6 risk model and the two-step triage strategy (2ST) to triage pregnancies of unknown location (PUL), and compare performance with the M4 model and beta human chorionic gonadotropin (BhCG) ratio cut-offs. Design. Model validation study. Setting. Eight UK hospitals with early pregnancy assessment units. Population. Women presenting with a PUL and BhCG >25 IU/L. Methods. Women were managed using the 2ST protocol: step 1 classifies PUL as low risk of ectopic pregnancy (EP) if presenting progesterone ≤2 nmol/L, M6 is used as step 2 in the remaining cases. We validated 2ST and M6 alone (with and without progesterone as a predictor: M6P and M6NP). M6 and M4 require the BhCG ratio over two days. Based on these models, we classified PUL as high risk for EP when the risk was ≥5%. We meta-analysed centre-specific results. Main outcome measures. Discrimination, calibration and clinical utility (decision curve analysis) for predicting EP. Results. Of 2899 eligible women, the main analysis excluded 297 (10%) women that were lost to follow-up. 16% (95% confidence interval 12-20) of women had presenting progesterone ≤2 nmol/L. The area under the ROC curve for EP was 0.88 (0.86-0.90) for 2ST and 0.89 (0.86-0.91) for M6P. Sensitivity for EP was 94% (89%-97%) for 2ST and 96% (91%-98%) for M6P. Both approaches had good overall calibration, with modest variability between centres. M4 and BhCG ratio cut-offs had inferior performance and lower clinical utility. Conclusions. The 2ST and M6P alone are the best approaches to triage PUL.