Field experiments were carried out at the experimental field of Rice Mechanization Center, Meet EI-Deeba, Kafer El-Sheikh Govemorate, Egypt. Two different types of Japanese combines harvesting machines, Yanmar model CA-385, cutting width 1400 mm, crawler travelling unit. adjusted pick tines and star wheels. Multi-purpose combine harvester Yanmar model CA-760, cutting width 2060 mm, crawler travelling unit, front reel, were tested at three different forward speeds of about (2.3, 3.2 and 4.5 km/h) three cylinder speeds (22.7, 28.1 and 32.1 m/s) and three moisture contents (16.3,13.6 and 10.9%) for wheat crop. The lowest values of header losses, threshing losses and shoe losses were (0.27,0.37 and 0.20%) and (0.35,0.27 and 0.17%) record­ed at grain moisture content of 13.6 %, cylinder speed of 28.1 m/s and forward speed of 2.3 km/h, for combines CA-760 and CA-385 respec­tively. Also the minimum values of total losses were (0.84 and 0.79 %) respectively obtained at forward speed of 2.3 km/h, cylinder speed of 28.1 m/s and grain moisture content of 13.6%, which are recommended for optimum harvesting wheat. At these conditions the criterion cost (109.3 and 94.3 LE/Fed), for the combines CA-760 and CA-385, re­spectively compared with manual harvesting followed by mechanical threshing and winnowing (192.55 L.EIFed).