The warm-up characteristics of a spark-ignition engine significantly affect fuel consumption and emissions from cars. A thermal imaging technique has been applied to measure the cylinder head surface temperature and piston surface temperature of an internal combustion engine simultaneously.The two-dimensional thermal images of the cylinder head surface temperature were viewed through an infra-red transmitting window mounted in the piston. The piston surface temperature was measured by painting black two small areas of the window's top surface. The similar thermal characteristics of the window material (silicon) to those of a normal piston and good heat transfer between the window and the piston provided realistic operation conditions. The mean and extreme values of the inlet valve, exhaust valve, two other areas of the cylinder head surface and window surface temperatures were measured from the thermal images during the first two minutes of the engine start. The influences of the engine speed, load, and cooling water upon the above temperatures were examined. The implication of the results on emission and combustion efficiency were discussed.