Piles are powerful geotechnical foundation elements which are suitable for most subsoil conditions where structure loads should be transmitted to deeper layers either to fulfill the required bearing capacity or to control the deformation to acceptable values regarding the structural serviceability requirements. In most cases, the pile foundations consist of group of piles. Realistic considerations of the pile group action regarding both the ultimate bearing capacity as well as the deformation behavior of the pile group are necessary to achieve a reliable, efficient and economic design. This paper deals with performance of pile groups under vertical compression loads. Simple analytical methods to estimate the settlement of pile groups will be presented and compared with enhanced three dimensional numerical analyses. The field monitoring of a well documented pile group under vertical compression loads and the feed-back of this information into the analyses procedure of the same pile group applying different analytical models will be demonstrated and discussed.