Though it looks like Pentax K-mount lenses should be adaptable to an EOS body, it turns out that the diaphragm coupling lever which sticks out from the back of the lens causes problems. On most EOS bodies you would have to remove this lever. However it is reported that EOS bodies which can take EF-S lenses [EOS 20D, EOS 30D, Digital Rebel (300D) and Digital Rebel XT (350D)], and maybe other APS-C format DSLRs can take adapted Pentax-K lenses without the need to remove the aperture coupling lever. There's is more room inside the EF-S capable body and the reflex mirror of APS-C sensor cameras is smaller, so there's less chance of interference. The adapters are available on Ebay for around $10-$40 (the more expensive ones have focus confirmation circuitry) and there are a number of sources. Some claim that they will work with any EOS body, not mentioning any modfication of the lens, but I'd be suspicious of such claims. Others warn that they only work with unmodified lenses with APS-C (crop sensor) DSLRs designed to accept EF-S series lenses.
