cam belts

I have just brought a 1992 318i could anybody tell me at what mileage the cam belt should be replaced,i have been told every 40,000 miles thanks GBB

The owners manual recommends every 60k miles, but many mechanics recommend 40k because if the belt brakes, you can loose the engine (pistons hitting valves, etc).

318i's with the M42 engine should also have the timing case profile gasket replaced.