Inspired bowling changes by Sussex's captain Chris Adams, which twice produced wickets in the first over and once in the third over, kept pulses racing, but rain had robbed the match of too much time - 137 overs - for there to be a positive outcome.
But it was a valiant effort by the Sussex attack especially as they were handicapped by the loss of Jason Lewry to a side strain.
The left-arm paceman still left his mark, bowling Craig Spearman with a yorker. In the preceding over Phil Weston had presented Matt Prior with the first of his catches.
But it had taken Sussex more than an hour to make that double breakthrough, by which time it had become apparent that Gloucestershire were not going to chase. However, caution can also be an insidious quality when trying to keep out the likes of James Kirtley, Mushtaq Ahmed and Sussex's other Pakistani signing Rana Naved-ul-Hasan.
They and the teenager Luke Wright kept plugging away and were rewarded as Gloucestershire's big hopes fell one after another.
Although the West Indies Test batsman Ramnaresh Sarwan managed to hang around for almost an hour and three-quarters he did not look comfortable, and his scratchy contribution ended when he hopped back in front of his wicket to a quicker ball from Wright.
Matt Windows and Alex Gidman had already departed and three other notably stubborn batsmen, Steve Adshead, Mark Hardinges and James Averis, soon followed, leaving Ian Fisher and Jon Lewis to negotiate a half dozen or so tricky overs with fielders clustered around the bat to the tense close.
Sussex had managed to add a further 67 to their overnight total, thanks in the main to Michael Yardy's third Championship hundred of the season.
Gloucestershire's Jon Lewis had reeled off 10 overs on the trot from the Sea End, a stint that included a burst of four for eight in 20 balls. Among his victims was Mushtaq, who became the 500th wicket of Lewis's first-class career. It also gave him his second five-wicket haul of the summer.
Yardy was last out, a tired drive ending up in Weston's hands at deep long-on to end a fine five and a half hour innings that had gone a huge way to setting up the exciting finish.