Search engine ranking

First off and FYI. I have SE friendly permalinks and I have a sitemap. I did some testing on my ranking for keywords and noticed that I rank on the first page for Yahoo and MSN for most, but not Google. I also noticed that the page the engine took me to was the home page EVERY time and not to the article page. It seems as though it read the site name and category, but not the article. Why is that and what can I do to change it?