Literature review on genetic alterations (microsatellite instability and loss of heterozygosity) in different types of cancer is presented. Microsatellite instability and loss of heterozigosity are significant processes in carcinogenesis. The evaluation of microsatellite instability in cancer patients might be of clinical importance as a prognostic and predictive factor. The most of up-to-date data available are on microsatellite instability in colorectal cancer. For other types of cancer, the number of publications on microsatellite instability is rapidly increasing.