The pilot reported that while in level cruise flight over an area of remote and unpopulated terrain, at an altitude of about 1,500 ft mean sea level, he noticed a dark flash in the upper left corner of the windscreen. He immediately pitched the nose of the airplane down and to the right to avoid another airplane. With his airplane operating normally and unaware that the two airplanes had contacted each other, he continued to his destination airport. During a postflight inspection, he noticed black marks and metal damage on the upper surface of the left wing. A postaccident examination revealed that the airplane had sustained substantial damage to the left wing and what appeared to be a black tire mark. The pilot reported no preimpact mechanical failures or malfunctions with the airplane that would have precluded normal operation. The other aircraft involved has not been identified.