Stealth is a skill in Ultima Online that by default is categorized under Thievery for obvious reasons. Stealth allows a character to move silently while maintaining invisibility, but it becomes much easier to detect such a character compared to Hiding.
A character must have at least 80.0 in Hiding to be able to use Stealth. Otherwise, the message You are not hidden well enough. Become better at hiding. will display.
It has been suggested by some players that you will not fail stealth checks with 60.0 Stealth and while wearing medable armor, though this might not cover the effect of passive (as well as active) detect hidden skill of the players around the stealther.
Raising Stealth: Stealth is an Activated Skill on the standard 10 second cooldown and is also check passively when attempting to move (walk) while hidden. Stealth is a difficulty based skill - attempting to move with higher level armor is more difficult and requires higher skill.