Antiquity has been considered the cradle of western civilization, including medicine. The role of diseases in the course of history has been stressed by several authors during the last few decades. The aim of this study is to survey the occurrence of diseases in antiquity. There are many obstacles to the study of the occurrence of diseases during antiquity. The most serious problem is the lack of reliable sources. Mostly we have to rely on written sources. Sometimes it is possible to supplement them with archaeological findings (e.g. bones and mummies). The defective sources give an unrealistically static picture of the occurence of diseases. Diseases must be seen as a dynamic relationship between populations and their environment. There is evidence suggesting great secular and regional variations in the occurrence of diseases during antiquity. Micro-organisms were by far the most serious threat to human health. We can be convinced that some diseases such as malaria, tuberculosis, mumps, cancer, trauma, etc, occurred during antiquity. Available sources do not, however, permit estimation of the frequency of these conditions in different populations and time periods. We have information of the occurrence of large-scale epidemics during antiquity, e.g. the plague of Athens (431-426 B.C.), the plague of Antonines (about 165-180 A.D.) and the plague of Cyprian (about 251-266 A.D.). However, the first definitely identified large epidemic (bubonic plague) was the plague of Justinian (starting in 542 A.D.).