BACKGROUND: The prognostic importance of dyskinesia after acute myocardial infarction is unknown, and recommendations have been made that dyskinesia be included in calculations of wall motion index (WMI). OBJECTIVE: To determine whether it is necessary to distinguish between dyskinesia and akinesia when WMI is estimated for prognostic purposes following acute myocardial infarction. DESIGN: Multicentre prospective study. PATIENTS: 6676 consecutive patients, screened one to six days after acute myocardial infarction in 27 Danish hospitals. INTERVENTIONS: WMI was measured in 6232 patients, applying the nine segment model, scoring 3 for hyperkinesia, 2 for normokinesia, 1 for hypokinesia, 0 for akinesia, and -1 for dyskinesia. Calculation of WMI either included information on dyskinesia or excluded this information by giving dyskinesia the same score as akinesia. MAIN OUTCOME MEASURES: Long term outcome (up to seven years) with respect to mortality. RESULTS: Dyskinesia occurred in 673 patients (10.8%). In multivariate analysis, WMI was an important prognostic factor, with a relative risk of 2.4 (95% confidence interval (CI), 2.2 to 2.7), while dyskinesia had no independent long term prognostic importance (relative risk 1.00; 95% CI, 0.89 to 1.12). For 30 day mortality dyskinesia had a relative risk of 1.23 (95% CI, 1.00 to 1.53) (p = 0.045). CONCLUSIONS: Echocardiographic evaluation of left ventricular systolic function shortly after an acute myocardial infarct gives important prognostic information, but the presence of dyskinesia only has prognostic importance for the first 30 days.