Munster (10) 19
Try: Murphy Con: O'Gara Pens: O'Gara 4
Montauban (3) 17
Try: Jonnet Pens: Mitu 4
Rowan Frist tackles Munster's Lifeimi Mafi at Thomond Park
Munster began their defence of the Heineken Cup in unconvincing fashion as they beat French newcomers Montauban in Pool One at Thomond Park.
Montauban led 3-0 early on but Munster enjoyed a 10-3 half-time advantage with the help of a Barry Murphy try.
A Sylvain Jonnet touchdown put the French side 14-13 in front but Ronan O'Gara replied with a penalty before Petre Mitu edged his side 17-16 ahead.
O'Gara kicked a 77th-minute penalty to secure a win for the relieved holders.
Montauban were playing their first match in the competition and fielded a much weakened side after making clear that their priorities lie in maintaining their top-flight status in their domestic league.
The visitors made a good start with a fifth minute long-range penalty by man-of-the-match Mitu.
The Romanian scrum-half then missed with a more straightforward kick.
The Irish province enjoyed much of the first-half possession but their progress was halted by a combination of handling errors and stubborn defence from their well-organised opponents.
Much of the play was scrappy as a nervous looking Munster outfit lacked the necessary composure to make their territorial advantage count.
Forward passes twice foiled attacking moves and then Keith Earls broke away after good work by Lifeimi Mafi but the full-back was penalised for holding on to the ball on the ground and the scoring opportunity was lost.
O'Gara took advantage of a Montauban infringement to level the scores with a 32nd-minute penalty.
Murphy then scored the champions' only try on 37 minutes, completing a move which involved Peter Stringer, O'Gara, Jerry Flannery and Doug Howlett, by stepping inside a tackle and grounding over the line.
O'Gara converted to earn his side a seven-point half-time lead.
After the break, Mitu missed with a penalty effort but made amends soon after by slotting the ball between the posts to reduce his side's deficit to four points.
O'Gara and Mitu traded penalties on 52 and 53 minutes before Montauban took the lead with a try by Jonnet.
Alan Quinlan's misdirected pass set up Jonnet and the winger won the race to the line to score.
Mitu was off-target with the conversion attempt and then O'Gara missed with a penalty.
O'Gara was successful with another kick but Munster's performance was still error-ridden.
Mitu landed a penalty in the 75th minute but O'Gara replied two minutes later to ensure victory, much to the relief of the 23,500 crowd.
Munster: K Earls, D Howlett, R Tipoki, L Mafi, I Dowling, R O'Gara, P Stringer, M Horan, J Flannery, J Hayes, P O'Connell (c), D O'Callaghan, A Quinlan, D Wallace, J Melck.
Replacements: D Fogarty, F Pucciariello, D Ryan, J O'Sullivan, M Prendergast, P Warwick, B Murphy.
Montauban: J Dalla Riva; S Jonnet, J Viard, R Jahouer, J Cassin; R Lespinas, P Mitu; B Balan, B Mach, N Adams, S Murray, R Frost, Y Caballero, M Raynaud (capt), M Clarkin.
Replacements: C Traversa, L DelBoulbes, S Florea, K Ghezal, A Battut, F Fortassin, J Laharrague
Referee: Wayne Barnes (England)