A wireline pressure control apparatus for use in an oil or gas well, comprising a grease injector having first and second tubes (10) and a bore (12), and a grease injection channel in communication with the bore for injecting grease between the outer surface of the wireline and the inner surface of the bore. The bore (12) has radial passages (15) at spaced apart locations providing a leak path for fluids between the inner surface of the bore and the outer surface of the tubes, allowing pressure to equalize. The radial passages are in fluid communication with one another outwith the bore.