It took a late try from hooker Jean Lonergan for Munster to grab an 11-10 win and lift the trophy for the second year running.
Coached this season by Donal O'Driscoll and Fiona Steed, Munster opened their campaign at Ravenhill last Saturday with a gritty 21-17 win over a committed Ulster side.
The visitors looked comfortable in the first half, with their solid lineout and elusive backs seeing them scoot ahead on the scoreboard.
Full-back Niamh Briggs popped over a penalty before winger Sandra Williams found enough space on the right to cross the whitewash, allowing Briggs to convert.
Ulster defended doggedly and partial credit must go to new coach Graham Cloke and manager Steven Hutton for having their side so well drilled.
The home side lost full-back Amy Davis to an early foot injury but Jessica Elliott from UUJ was an able replacement and a penalty from Ireland international Jo O'Sullivan steadied nerves.
However, the loss of winger Cathy Craig to a yellow card, five minutes before half-time, hit Ulster badly and off another well-executed lineout move, flanker Kate O'Loughlin bulldozed through for Munster's second try.
The champions, though 18-3 in front, looked under a bit of pressure as Ulster, who had the wind at their backs in the second half, snuck over for a try from replacement Clodagh McCool from Derry.
Ironically, the score stemmed from Ulster's only lineout win of the second period and O'Sullivan neatly added the conversion for 18-10.
When Briggs was sent to the sin-bin, the home side sensed an upset and they duly cut the gap to a single point when good continuity from their backs and forwards resulted in a try under the posts for winger Eliza Downey.
O'Sullivan's conversion pushed Ulster onto 17 points and set up a grandstand finish. Yet Munster, right from the restart, worked the ball through their experienced pack and gained a penalty which the returning Briggs crucially sent through the uprights.
Connacht, who finished third in last season's tournament, have a number of new players involved in the squad this term.
They had nine debutants for last weekend's opening match at home to Leinster, a statistic which pleased head coach Lyndon Jones.
He said: "We are delighted with the new caps in the squad this season. It is a great sign of the development of the game within the province that Creggs RFC, Westport RFC and NUIG RFC have a strong presence on the panel."
But the fresh input was not enough to overthrow Leinster at the Sportsground as the pumped-up visitors impressed with a 41-0 victory.
Both Claire Molloy, with her line-breaks, and Helen Jones, with her ball carries, caught the eye for Connacht.
Tries from international duo Grace Davitt and Fiona Coghlan saw Leinster establish an early 10-0 lead and further touchdowns from Tania Rosser, Ciara Kennedy from Navan and Coghlan again left Connacht trailing by 29-0 at the break.
Leinster's strength in depth really came to the fore on the resumption as coach Ray Ward unloaded his bench and Connacht's inexperience and tired limbs saw them ruthlessly exposed.
Leinster's sixth and seventh tries followed as Yvonne Nolan got on the scoresheet and the aforementioned Kennedy notched her second try.
All that leaves Leinster in pole position to qualify for the championship final, which will be staged by Ulster on Saturday, October 25.
Their clash this Sunday with Munster will be some tussle, while Connacht and Ulster's meeting at Tuam RFC gives both sides a chance to post their first wins and challenge for a final place.
2008/09 WOMEN'S INTERPROVINCIAL CHAMPIONSHIP:
ROUND ONE RESULTS (Saturday, September 13) -
Ulster 17 Munster 21, Ravenhill
Connacht 0 Leinster 41, The Sportsground
ROUND TWO FIXTURES -
Saturday, September 20:
Connacht v Ulster, Tuam RFC, 1.30pm
Sunday, September 21:
Leinster v Munster, Lakelands Park, Terenure College RFC, 2.30pm
ROUND THREE FIXTURES -
Saturday, October 18:
Munster v Connacht; Leinster v Ulster