Title: Cosmic Ray Showers with Anomalous Longitudinal Profile Author: Jiří Blažek Department: Institute of Particle and Nuclear Physics, Faculty of Mathematics and Physics, Charles University Supervisor: RNDr. Petr Trávníček, Ph.D., Institute of Physics ASCR Abstract: The aim of this work was to study high-energy cosmic ray showers with anomalous longitudinal profiles generated by Monte-Carlo simulation and subse- quently use the acquired analysis techniques on results from the Pierre Auger Observatory (PAO) in Argentina. Firstly, a short introduction of various de- scriptions of the extensive air showers was given. Then a systematic analysis was performed on approx. 7 × 105 simulated showers with three different tech- niques. A brief explanation of the functionality of the PAO was given, then the importance of monitoring the immediate state of the atmosphere using the Shoot- the-Shower program was elucidated and the FRAM telescope was described in detail. FRAM enabled an identification of showers with a clear atmospheric back- ground, this sample of showers was then analyzed and several interesting events warranting a further study were chosen. Keywords: Pierre Auger Observatory, Extensive Air Showers, Chemical Compo- sition, Anomalous Longitudinal Profile, Gaisser-Hillas Function