This article presents problems connected with the system of operation of agricultural tractors. The aim of this article was to determine the level of reliability of used agricultural vehicles in the aspect of needs for technical services in the authorized service station. The quantitative structure of 6127 repairs carried out by an authorized service regarding 1731 tractor pieces sold to users by a distribution company has been described in a monthly arrangement. The analysis encompasses the arrangement of the number of technical services in a percentage array in the years 2003-2014. The data analysis shows that the trend line determined for post-warranty services has varied over a span of the analysed period. The analysed services had a large amplitude of random fluctuations. The acquired seasonal indexes values prove the cyclical changes of demand for servicing in subsequent months. The tendency in the behaviour of the users who own modern agricultural tractors, to more and more common use of authorised services when it comes to carrying out technical services of the operated equipment was confirmed.