Arsenal 0-3 Inter Milan
Arsenal's Champions League campaign got off to the worst possible start as they were humbled at home by last season's semi-finalists Inter Milan.
The Italians destroyed Arsenal with a spectacular first-half display in which they scored three times and could have had more.
Julio Ricardo Cruz, Andy van der Meyde and Obafemi Martins grabbed the goals, with Thierry Henry seeing a penalty wonderfully saved by Francesco Toldo to compound the Gunners' misery.
Arsene Wenger's men had no answer to their awesome opponents and must now try to get the defeat out of their system before the trip to Old Trafford to face Manchester United in the Premiership on Sunday.
22 mins: Cruz puts Inter ahead with a precise finish
25 mins: Van der Meyde doubles their advantage
32 mins: Henry's penalty is saved low to his left by Toldo
41 mins: Martins wraps up the points for Inter with a fine finish
Arsenal had started the game brightly enough, looking keen to end their run of five home games in the Champions League without a win.
And Freddie Ljungberg should have put them in front after 15 minutes, but the Swede could only shoot straight at Toldo from 12 yards with just the keeper to beat.
Seven minutes later the game burst into life as Inter accelerated into a gear Arsenal simply could not live with.
Martins headed the ball into Cruz's path in the inside left channel, and the Argentine striker bore down on goal before delicately chipping over the advancing Lehmann to put his side ahead.
Three minutes later van der Meyde doubled Inter's lead. Kily Gonzalez's deep cross from the left brushed off Sol Campbell's head, and the Dutchman lashed the ball on the volley past the despairing Lehmann.
Thierry Henry misses his first-half penalty
In truth, the German goalkeeper should have done better, but the stunned silence that radiated around Highbury gave a clear indication that this was not going to be Arsenal's night.
The Gunners did have a chance to half the deficit just after the half hour mark, but after Materazzi had been harshly adjudged to have pushed Ljungberg, Henry saw his penalty brilliantly turned around the post by Toldo.
By this time, Martins was causing Arsenal palpitations every time he had the ball, and he got a well-deserved goal with a firm finish past Lehmann four minutes before the break after great skill from Emre.
Perhaps with Sunday's Premiership game in mind, Wenger brought on Dennis Bergkamp and Kanu for Gilberto and Robert Pires after the hour mark.
The Nigerian had a chance to net a consolation nine minutes from time, but Toldo kicked his close-range effort away after good work from Ashley Cole.
Inter substitute Mohamed Kallon nearly made it four in stoppage time, but his right-foot finish struck the inside of the post.
Arsenal must now try to take maximum points from Dynamo Kiev and Lokomotiv Moscow and end their record run of six home games in Europe without a win.
Arsenal: Lehmann, Lauren, Campbell, Toure, Cole, Ljungberg, Vieira, Silva (Kanu 64), Pires (Bergkamp 64), Wiltord (Parlour 78), Henry.
Subs not used: Stack, Keown, Edu, Cygan.
Inter Milan: Toldo, Javier Zanetti, Materazzi, Cannavaro, Cordoba, Van der Meyde (Helveg 69), Emre (Lamouchi 66), Cristiano Zanetti, Gonzalez, Cruz (Kallon 84), Martins.
Subs not used: Fontana, Luciano, Adani, Buruk.
Referee: Manuel Enrique Mejuto Gonzalez (Spain).