The electronic medical record has evolved from a digital representation of individual patient results and documents to information of large scale and complexity. Big Data refers to new technologies providing management and processing capabilities, targeting massive and disparate data sets. For an individual patient, techniques such as Natural Language Processing allow the integration and analysis of textual reports with structured results. For groups of patients, Big Data offers the promise of large-scale analysis of outcomes, patterns, temporal trends, and correlations. The evolution of Big Data analytics moves us from description and reporting to forecasting, predictive modeling, and decision optimization.