This course addresses the key principles of research aimed at assessing the effectiveness and safety of pharmaceuticals. We begin by exploring the role of effectiveness research and stakeholders who need this evidence and explore the common observational designs that are used with real world data to generate real world evidence about safety, effectiveness and comparative effectiveness of drugs. We discuss confounders and biases that must be addressed and methods for overcoming these challenges both in the design and in the analysis of observational studies. We briefly address pragmatic trials as a source of effectiveness and safety information. The course concludes with examples of published studies illustrating good practices.