OBJECTIVE to compare the results of the Alvarado score with the surgical findings and the results of the histopathological examination of the appendix of patients operated on for acute appendicitis. METHODS we conducted an observational study with a cross-sectional design of 101 patients aged 14 years and over undergoing emergency appendectomy. The evaluation comprised the Alvarado score, gender, age, ethnicity and time of evolution. We obtained data regarding the surgical aspect of the appendix, postoperative complications and the result of the histopathological examination. The pre-established confidence interval was 95%. We calculated sensitivity, specificity, positive and negative predictive values of the score, and performed an analysis through the ROC curve. RESULTS we found a statistically significant (p=0.002) association between the Alvarado score and the diagnostic confirmation using a cutoff score of six or greater, with a sensitivity of 72% and a specificity of 87.5%. A score greater than or equal to six showed a greater tendency to present more advanced stages of acute appendicitis in both surgical and histopathological findings when compared with a score lower than six. Males presented greater chances of complications when compared with females (p=0.003). CONCLUSIONS the Alvarado score proved to be a good method for diagnostic screening in acute appendicitis, since scores greater than or equal to six are associated with a higher probability of diagnostic confirmation and more advanced stages of the acute disease.