BACKGROUND: Several studies have analyzed the correlation between digital and standard videotape echocardiographic images. The advantages of digital echocardiography are a faster exam, lower costs and a greater number of exams performed. Our study's aim was to evaluate the correlation and agreement between cardiac dimensions measured by M-mode and two-dimensional echocardiography, using the Echo Off Line free software, and by standard echocardiography. METHODS: This was a cross-sectional, randomized study, in 56 patients, whose images were acquired during echocardiographic examination. Left ventricular systolic and diastolic diameters, septal and posterior wall thicknesses, and left atrial and aortic diameters were measured using the Echo Off Line program. These measures were compared to those acquired using the standard method by a different sonographer, through correlation and agreement analysis as described by Bland and Altman. Values of p<0.05 were considered significant. RESULTS: The correlation index between the methods varied from 0.85 to 0.98 (Pearson's correlation coefficient) for all the variables studied. The analysis showed that there was good agreement between the methods for most of the measures, the mean difference being close to zero. The variability in absolute values, for most measures, did not reach clinical significance. The method's reproducibility (intra-observer) was adequate. This measurement tool demonstrated correlation indices similar to those in the literature consulted, as well as adequate reproducibility indices for intra-observer measures. Its low cost, compared to that of imported workstations on the market, means it can be widely used without significant costs (free software). CONCLUSION: There is a direct correlation and good agreement between M-mode and two-dimensional echocardiographic measures of cardiac dimensions obtained by the Echo Off Line program and by the standard videotape-based method. The Echo Off Line program can be used routinely in echocardiography laboratories.