Objective: Despite recent guidelines proposed by the World Health Organization (WHO), the operational definition of maternal near-miss (MNM) is still heterogeneous. This study aimed at evaluating the pros and cons of three instruments in characterizing MNM cases. The performance of two of the three instruments was also investigated vis-a`-vis the WHO criteria. Study design: A retrospective chart review study was carried out in a tertiary maternity hospital in Rio de Janeiro, Brazil. The medical records of 1163 obstetric hospital admissions from January to December 2008 were reviewed. Cases were first classified as ‘positive’ or otherwise according to the WHO, Waterstone and literature-based criteria. A descriptive analysis was then carried out focusing on divergent classifications. Finally, diagnostic properties of the Waterstone and the literature-based criteria were calculated taking the WHO criteria as reference standard. Results: There were eight maternal deaths, 157 cases classified as ‘positive’ by at least one of the three approaches and 998 cases without severe morbidities. Twenty-seven cases of MNM were detected according to the WHO criteria, whereas the Waterstone and the literature-based criteria identified 123 and 153 cases, respectively. Among the 130 cases identified as ‘negative’ by the WHO criteria and ‘positive’ by the Waterstone or literature-based criteria, 119 presented hypertensive disorders (91.5%). Additionally, four cases were identified exclusively by the WHO criteria because of acute thrombocytopenia (platelets < 50,000). Estimates of sensitivity, specificity, accuracy and negative predictive values were all above 75% for the Waterstone and literature-based approaches, but both criteria presented positive predictive values (PPV) below 60% even with high magnitudes of MNM. Conclusion: These results underline that different approaches entail heterogeneous estimates of MNM. The Waterstone and the literature-based criteria are not suitable for a definitive diagnosis of MNM in view of their low PPV, but they seem adequate as a first approach in investigating MNM. While negative results by both alternative criteria virtually rule out MNM, a positive result would require a reassessment using the WHO criteria to confirm the diagnosis of maternal near-miss.