A process cartridge detachably mountable to a main assembly of an electrophotographic image forming apparatus includes a cartridge frame; an electrophotographic photosensitive member; process means actable on the photosensitive member; a first cartridge guiding portion for being guided by a main assembly guide provided in the main assembly of the apparatus when the process cartridge is mounted to the main assembly of the apparatus, the first cartridge guiding portion being provided at one end, with respect to a mounting direction in which the process cartridge is mounted to the main assembly of apparatus, of the cartridge frame; and a second cartridge guiding portion for being guided by the main assembly guide provided in the main assembly of the apparatus when the process cartridge is mounted to the main assembly of apparatus, the second cartridge guiding portion being provided at the other end, with respect to the mounting direction, of the cartridge frame, wherein when the process cartridge is mounted to the main assembly of the apparatus, the first and second cartridge guiding portions are at different heights.