I believe the current stance is that weed may cause cancer. It contains many of the same carcinogins (in higher concentration) than cig's however there has yet to be a reliable study connecting cancer and weed smoking directly. This doesn't mean that there is no link, because there has yet to be study disproving a link as well. I believe it has been disproven that emphaseama (sp?) and weed have a link. Something about the chemicals that cause emphaseama are not in weed smoke. I'm too lazy to find the study that found that one right now... maybe later.