Rugby: Dan Parks' points save Warriors
Paul Marshall's fine breakaway try put Ulster ahead but Parks reduced the deficit to 5-3 with a 13th-minute penalty and that is the way it remained until the interval.
Ian Humphreys' boot matched Parks and helped Ulster re-establish their five-point cushion at 11-6 but a Graeme Morrison try and three further drop-goals from Parks put the hosts in control.
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Hide AdJamie Smith crossed for a late consolation try for the visitors but it was not enough to prevent a fourth consecutive loss.
Both sides desperately needed the points – Ulster to ensure a Heineken Cup place next season above Connacht, and Glasgow to stay in the running for a Magners League play-off spot.
The win puts Glasgow into third spot in the league table, three points ahead of Edinburgh, who take on Newport-Gwent Dragons at Rodney Parade tomorroe evening (5.05pm).