India 242-5 (47 ovs) bt Pakistan 239-7 (50 ovs) by 5 wkts
Dhoni took the Man of the Match award for his aggressive 63
Mahendra Dhoni and Yuvraj Singh hit half-centuries to inspire India to a five-wicket win over Pakistan in their opening one-day match in Guwahati.
They put on 105, the aggressive Dhoni hitting eight fours in his 63, while Yuvraj fired six fours and a six in 58.
Both fell near the end but India got to their 240 target with 18 balls left.
Salman Butt gave Pakistan a good start with 50 from 57 balls and Mohammad Yousuf, dropped on nine, hit eight fours in a battling unbeaten 83.
The victory gave the hosts a vital early edge in the five-match series, which continues in Mohali on Thursday.
Pakistan's total of 239-7 having opted to bat first did not look sufficient, despite a slow pitch that made shot-making difficult.
After Sachin Tendulkar was lbw to a Shoaib Akhtar slower ball in the third over, it appeared that an Indian victory would not be straightforward.
Gambhir (44) twice edged Shoaib - noticeably overweight in his second match back after injury problems and a 13-game ban - between keeper and slip to the boundary early in his innings.
But he and fellow left-hander Sourav Ganguly (39) slowly came to terms with the surface with a third-wicket stand of 82 spanning 14 overs.
They were progressing serenely until Ganguly beaten by a throw from Butt at backward square-leg.
Four overs later Gambhir missed a straight one from Shahid Afridi that bowled him around his legs with 127 still needed.
But Dhoni, the man of the match, signalled his intentions by flashing at his first ball, which fizzed off the outside edge to the boundary, and the batting side were soon firmly in command again.
Yuvraj, who survived a confident lbw appeal from spinner Abdur Rehman on 35, wafted the next ball effortlessly over mid-wicket for six to keep his team well ahead of the rate.
He was first of the pair to 50, from 66 balls, Dhoni following suit in the next over, and the searing boundaries continued as the 100 stand came up in 129 balls.
With 22 needed from 42 balls, Yuvraj top-edged a sweep to fine-leg and the requirement was 15 from 35 when Dhoni was smartly caught behind off the persistent Shoaib.
Butt was needlessly run out having completed a fine fifty
There were a couple more moments of anxiety before Robin Uthappa thumped Shoaib down the ground for four and advanced down the pitch to slice the winning boundary through third man.
When Shoaib Malik elected to have first use of the pitch, Butt played some fluent strokes with the field up for the powerplay overs.
Kamran Akmal was not able to score as freely and succumbed playing an ungainly stroke across the line.
However replays suggested that English umpire Ian Gould - resplendent in old school colonial-style panama hat - was incorrect as the ball pitched outside leg-stump.
Pakistan were looking good but an unnecessary run out just after the drinks break forced them to rebuild.
Having reached 50 from 56 balls, Butt miscued to mid-off but set off for a perfectly realistic single, only to find Younus Khan rooted to the non-striker's end.
With off-spinner Harbhajan Singh and slow left-armer Murali Kartik operating in tandem the scoring slowed, 16 overs passing by without a boundary.
There are still four games to go and I'm sure we can get back into the series
Yousuf was reprieved when he got a leading edge playing against the spin of Kartik but Ganguly, running back towards mid-off, could not cling on to the chance.
Younus also felt the urgency to accelerate the scoring but succumbed, lofting to long-off for 25.
It took until 35th over for the first six of the innings, a brutal heave over long-on from Afridi on his way to a 32-ball 31, but when spin returned problems mounted for Pakistan.
Having butchered another boundary, Afridi was hopelessly deceived in the flight by Tendulkar and was almost nearer the bowler's end than the crease as Dhoni took off the bails.
Worse was to follow as Malik, wearing eye-catchingly luminous green pads, fell to an eye-catchingly bad shot, hoiking a full toss from Tendulkar straight to the fielder on the mid-wicket boundary.
Yousuf ground out a 68-ball half-century, the 200 coming up in the 46th over, but the lack of significant support from his middle-order colleagues proved decisive.