Peterborough's search for their first point of the season continues after Sam Baldock's double ended Bristol City's poor start away from home.
City had not scored away from home but struck when Baldock converted a poor backpass from Posh's Mark Little in the second half.
Baldock, who came close joining Posh last summer, then struck following a pass from Albert Adomah.
Posh's Lee Tomlin scored a penalty after he was fouled by Martyn Woolford.
But there was no equaliser for the home side and Darren Ferguson's team remain the only outfit in the Football League without a point.
With six games of the season gone, Posh are already six points adrift of safety as their worst start to a season continues.
Posh conceded five against Burnley on Saturday and Ferguson made three changes to the backline, with Nathaniel Knight-Percival coming in for his league debut along with Gabriel Zakuani and Kgosi Ntlhe.
Tomlin and George Boyd went close for the home side as they pushed for the opener, but Posh's Robert Olejnik was the first keeper to make a meaningful save, denying Baldock after the restart.
Olejnik could not stop Baldock after he capitalised on the error from Little, who was lucky to stay on the pitch just minutes later following an awful challenge on Liam Fontaine.
After Baldock's second, Tyrone Barnett was lucky to escape a red card for a dangerous challenge which saw Greg Cunningham stretchered off as the home team lost their discipline.
And despite Tomlin's penalty, City ended the match celebrating their fifth win in six league visits to London Road.