One of the main defects in rail steel is a defect on the rolling surface of the rail head. A sign of the defect appearance is delamination and spalling of the metal on the rolling surface. The development of this type of defect to a length of more than 25 mm and a depth of more than 4 mm requires a decrease of the train speed up to 70 km·h-1 , and with a depth of more than 8 mm - to 25 km·h-1 . Reducing the speed significantly affects the quality of service and railway performance. As a result, there is a disruption in the accuracy of train traffic, which subsequently leads to material costs for restoring the movement of trains at set speeds. The primary task of the study presented in this article is the collection and analysis of statistical information on the Latvian Railway defective rails in the period from 2011 to 2021. A secondary task is to investigate the causes of the appearance of rail defects under code X 10.1. The research process included: detection of these defects on the Latvian Railway using a modern ultrasonic flaw detector of the “RDM-24” type, determination of the metal hardness (EN 13674- 1:2011 standard 350-390 HB) in the rail head and on the rolling surface using a certified modern device “Tinius O Olsen” Firmware Version 1.07, FH - 31 Series as well as the study of the chemical composition of the rail head using the optical emission analyzer PMI - Master PRO and determination of the microstructure of the metal in the rail head. At the final stage, to compare the results obtained in an independent certified laboratory, based on the results of the research to draw conclusions about the causes of this type of defect.