The package says after 10 uses there will be a noticeable difference and it works best on blonde hair. I was really impressed with this stuff! I definitely notice a difference, particularly on the bottom half of my hair since it is lightest. I haven't died my hair in over a year so the top half is darker because of my roots growing out. I have started using it only on the tops of my hair to lighten it up a bit more. I'm planning on dying my hair pink and this is great alternative to bleaching.
I would definitely consider buying this stuff full size. I would recommend it to anyone who wants to easily lighten their hair a shade or two. This stuff is awesome!