I am using Canon BCI 6 cartridges and find that it is economical to use third party cartridges instead of refilling them. There are two types - store brands and on-line brands. Store brands are still expensive and cost around 7$. However on Amazon you can find "Abacus" brand for 2$ It is worth it if you need to order all of them (all colors). I didn't find any difference in quality. Found it on "http://all-about-my-money.com/?p=17" for more details.