It is anticipated that the ITRF97 version of the realization of the International Terrestrial Reference System (ITRS) will be accomplished at the end of 1998. This paper will present the most important results of the ITRF97, underlying the expected improvements with respect to the previous ITRS realizations. Moreover, the ITRF combinations are critically based on colocation sites which are of primary importance for connecting the individual terrestrial reference frames and the inter-technique quality assessment. A special attention will be focused on the quality of the colocation sites in ITRF97 in order to evaluate their impact on the quality of the ITRF97 combination.