This report contains a compari on between two rainfall-runoff models, namely the Swedish HBV model and the Chinese Xinanjiang medel, together with some examples of applications of the two models. It further contains a more detailed study of automatic calibration schemes for the HBV model, as well as the development of a new optimization scheme. The work was carried out by Dr ZHANG Xingnan, on a six month research leave from the Hohai University in Nanjing, China. Dr ZHANGs stay at the Swedish Meteorological and Hydrological lnstitute was made possible by a grant from the Swedish lnstitute. Dr ZHANG worked in close cooperation with the staff of the SMID. The work presented herein was done within the framework of the HBV-2000 project. This project is a revision of the HBV model structure, which has remained relatively unchanged since its development some twenty years ago.