The objective of this book is to make its readers better informed and more critical consumers of clinical research and to help them recognize the strengths and the weaknesses of scientific publications. In doing so, the reader will be able to distinguish patient-important and methodologically sound studies from those having limitations in design, conduct and interpretation. This book updates and expands the first edition of this text, released in 1994. The previous edition was only available in Swedish. There are no prerequisites for reading this book. The text is basic and has no statistical formulas. Key take-home messages are listed at the end of each chapter. The large number of cartoons has two purposes: First, to make the text easier to read and generate a few laughs and, second, to underscore specific points, sometimes in a provocative way.