A pilot entered a Tower Controller assigned downwind for Runway 4 and had a near miss with an aircraft on a Tower assigned downwind for Runway 22. ATC told the pilot to question his clearance.

Narrative

I approached the airport from the east. The ATIS announced Runway 4 active; winds 3 KTS. Tower assigned me a right downwind for Runway 22. I wrote down the clearance and read it back as such. Then; I circumnavigated the airport to the north and made a 45 degree entry accordingly. Just after entering the downwind; I observed a single engine Cessna coming in the opposite direction; slightly to my right (closer to the runway). I turned left and descended to move away. The other aircraft the tower; 'Where did that Bonanza come from?'. The Tower replied 'From the East' and upon being told that we had passed opposite directions; asked me what I had done. He asserted I had been assigned a left downwind for Runway 4. I replied that I had been assigned a right downwind for Runway 22; had read it back; and had circumnavigated. The Controller said to query a dubious instruction next time. Upon his new instruction; reversed course; joined a downwind for Runway 4; and landed without further incident. In retrospect; I had doubted the clearance but with the wind so light; believed a runway change had taken place; I had also been reluctant to question the authority of the Controller. In an odd coincidence; later the day; I departed the same airport and assigned a different runway from two preceding aircraft. I certainly questioned the assignment that time. Next time reading back is not enough. Call attention to a clearance that seems inappropriate.