As far as I know, you need several sessions for complete removal. Between each session you have to wait 3 months for the skin to recover - just the same as when you get a tatt in the first place. In that time period, the skin heals and the broken up ink is washed away by natural skin rejuvenation {god bless red underline spell checker for that one). Some ink colours such as yellow are harder to remove, and black ink is the easiest. I am pretty sure I heard that different colour inks need different lasers, or different strengths of laser. Complete removal is possible. Also with some cover-ups, it it is better to thin down the tatt first with a couple of sessions. That said, this is just what I have learnt from telly - so it may all be bollox