Sherborne was one ahead of Switzerland's Paolo Quirici and two clear of six players - Sam Torrance, Ian Spencer, John Bickerton, Russell Claydon, the Italian Costantino Rocca, and Domingo Hospital, of Spain, by two.
Sherborne went round the 7,114-yard course at the Gardagolf Country Club without a bogey on his card, despite damp and chilly weather which forced officials to allow preferred lies on the fairways following Wednesday's heavy rain.
Sherborne holed out from 45 yards with a sand wedge at the 11th hole for an eagle three, and two holes later sank a 20-foot putt for a birdie three.
Bickerton - playing on the European Tour for the first time this year - was also satisfied with his round. The 23-year-old was working as a sheet metal worker last year and could play little golf.
Torrance, who has played in the last six Ryder Cup matches and badly wants to figure in the next at The Belfry in September, shot his 69 despite suffering from nosebleeds.
David Gilford, who has won two tournaments this year, shot a 72, while Barry Lane, the leader in the Ryder Cup points table, had a 76.
KRONENBOURG OPEN (Salo, Italy): Leading first-round scores (GB or Irl unless stated): 67 A Sherborne. 68 P Quirici (Swit). 69 R Claydon, C Rocca (It), D Hospital (Sp), J Bickerton, S Torrance, I Spencer. 70 M Moreno (Sp), J Sewell, P Smith, J Haeggman (Swe), S McAllister, Y Beamonte (Sp), T Gogele (Ger). 71 J Berendt (Arg), C Hardin (Swe), T Giedeon (Ger), S Bowman (US), M McLean, M Sludds, G Orr, A Binaghi (It), L Jones, C Cassells. 72 M Pendaries (Fr), G Hjerstedt (Swe), D Gilford, H Clark, P McGinley, C Raulerson (US), A Cejka (Ger), R Willison, D Williams, P Talbot, R Boxall, C Whitelaw (SA), S Watson, B Marchbank, A Hunter. 73 R Drummond, A Bossert (Swit), T Pernice (US), G Ralph, M Florioli (It), A Lebouc (Fr), D Edlund (Swe), R McFarlane, M Guzman (Arg).