Gloucestershire 176 for 6 trail Leicestershire 421 (Hill 121, Mike 54, Worrall 5-79) by 245 runs
Lewis Hill's second first-class century and four wickets from Chris Wright put Leicestershire firmly in command at Bristol as Gloucestershire closed day two 176 for 6 replying to 421.
Hill took his overnight 77 to 121 as Leicestershire ground out 144 overs with Ben Mike also making 54, his third first-class fifty, as the Foxes posted their second-highest total at Bristol.
Wright then helped plunge Gloucestershire from 99 for 1 to 121 for 6 in a calamitous half hour for the hosts that puts their unbeaten start to the season in serious jeopardy.
All was well with Gloucestershire's reply as Chris Dent made a fourth fifty of the summer. But he felt for one sent across him from Wright and edged behind for 53 after James Bracey, on 27, played across the line and was lbw to Callum Parkinson.
Ian Cockbain couldn't get his bat down in time to a full straight delivery from Wright and was lbw for a third-ball duck. Tom Lace, only 4, then nudged at Dieter Klein and edged low to third slip before Ryan Higgins was squared up by Wright and lbw for 5 struck on the back pad.
It was a wonderful final session to another excellent day for Leicestershire who resumed 264 for 4 and, though they were only able to claim one more batting point, built well through Hill.
When Hill made 126 against Surrey in just his second first-class match in 2015 his career was all before him. Since then only the 2017 season - 554 runs at 30 - has been remotely noteworthy. But talent has clearly never deserted him and he arrived with four half-centuries and a 47 in six innings this season and here reached a long-awaited hundred in 176 balls.
A flashing cover drive off Josh Shaw, to a delivery that was by no means a half-volley, was the stroke of the match so far but he fell just short of his career-best, driving at one from Higgins angled in that took out his off stump.
Mike passed fifty in exactly 100 balls but Leicestershire lost their last four wickets for 28 as Dan Worrall finished with 5 for 79 - an eighth five-for of his career and first for Gloucestershire.