In 1982, The Braves won 13 in a row to begin the season.
In MLB, it is the 1982 Atlanta Braves and 1987 Milwaukee Brewers with 13 consecutive wins to start the season.
10 games, by 1993-94 Toronto Maple Leafs and 2006-07 Buffalo Sabres
New Jersey Nets with an 0-18 losing streak
New Jersey Nets. 2009-2010.
Through the 2009 season, 21 games by the 1988 Baltimore Orioles. And the Chicago Cubs lost 14 games to start the 1997 season.
15-0 by the Washington Capitols in 1948-49 season (November 3-December 4, 1948) 15-0 by the Houston Rockets in 1993-94 season (November 5-December 2, 1993) a tie
at&t park with Barry bonds on the SF Giants
The longest high school baseball winning streak is 89, held by Portsmouth High School (NH) which ended April 30, 2012. The longest active is Martensdale-St. Mary's High School, which is at 87 (their season doesn't start until May 21). The MLB record is 26 set by the 1916 New York Giants.