A second-half goal from Fredy Guarin saw Inter edge city rivals Milan today evening to pick up a third consecutive win and go clear at the top of Serie A.
The Colombian midfielder broke the deadlock in the 58th minute with a left-footed shot that beat Milan goalkeeper Diego Lopez.
Mario Balotelli, playing in his first league game since returning to Milan on loan from Liverpool, entered the action four minutes later and he rattled the left-hand post from 25 yards.
Inter held on to earn victory in the first San Siro showdown of the season.
The win sees Inter, who were hosting the game, move two points clear at the top of the table - a position they had not held alone for five years.
Sassuolo saw their perfect start to the campaign come to an end as they could only draw 2-2 at home to Atalanta.
Mauricio Pinilla put Atalanta ahead on 13 minutes with an overhead kick to beat Sassuolo goalkeeper Andrea Consigli.
Francesco Magnanelli equalised in the 22nd minute with a 30-yard drive but 11 minutes later, Pinilla struck past Consigli to put Atalanta back in front. Seven minutes later, Sassuolo equalised through Antonio Floro Flores' 25-yard volley.
Napoli, meanwhile, are still searching for their first league win in 2015-16 after they drew by the same scoreline at Napoli.
Riccardo Sapponara put the home side ahead early on, but Lorenzo Insigne equalised for Napoli in the seventh minute, before Empoli hit back in the 18th minute through Manuel Pucciarelli.
Napoli, whose new coach Maurizio Sarri was in charge of Empoli for the previous three seasons, pulled level five minutes after the restart when Manolo Gabbiadini set up Allan in the box and his shot towards the near post beat Lukasz Skorupski.
Carpi were denied a first Serie A win as they also drew 2-2, with Uros Djurdjevic notching a late equaliser for Palermo.
The newly-promoted side looked to be on track for the landmark victory when Marco Borriello and an own goal from Palermo defender Roberto Vitiello negated Oscar Hiljemark's opener. But Djurdjevic had other ideas, heading home Achraf Lazaar's cross two minutes from time.
In the fourth 2-2 result of the day Torino preserved their unbeaten start at Verona.
Acquah salvaged the draw late into the second half after Juanito restored Verona's advantage in the wake of Torino's Daniele Baselli cancelling out Luca Toni's fourth-minute strike.
Two second-half goals from substitute Alessandro Matri saw Lazio beat a resilient Udinese 2-0 in Rome to pick up their second win of the season.
Sampdoria's home game against Bologna this afternoon had to be postponed due to heavy storms in Genoa. The teams will try again tomorrow.