A plate heat exchanger comprises a plurality of heat exchanger plates (1). The plates are provided beside each other and permanently joined to each other to form a plate package having first plate interspaces and second plate interspaces. Each plate has a heat transfer area (20) and four porthole areas (21-24) defined by a porthole edge (25). Each of the porthole areas comprises an annular flat area (31) located at one of a primary and secondary level, and a set of inner portions (32) on the annular flat area at the other of the primary and secondary level. Each inner portion has an inner part adjoining the porthole edge and an outer segment adjoining the inner part and having an angular extension of at least 180°. The outer segment has a continuous contour and a radius R, which is allowed to vary within the range 0.8R≦R≦1.2R.