Leicester Tigers' Alesana Tuilagi breaks through to score his second try of a hat-trick
A try by Eliota Fuimaono-Sapolu in the dying seconds secured Gloucester a record-breaking draw at Welford Road.
Olly Morgan grabbed an early try for the visitors which was swiftly cancelled out by Scott Hamilton.
Fuimaono-Sapolu gave Gloucester the interval lead but a 17-minute hat-trick from Alesana Tuilagi had appeared to put Leicester in charge.
The visitors hit back through Andy Hazell and Tim Molenaar with Billy Twelvetrees going over for the hosts.
Leicester stay top of the table after the highest-scoring draw since the Premiership began.
It was also the most points the Tigers have conceded in a home league game.
Meanwhile, battling Gloucester continue to eye a top-four finish.
From the very start both sides played open attacking rugby with Freddie Burns converting Morgan's effort and Toby Flood adding the two points after Hamilton's try.
A Flood penalty put the hosts ahead before Fuimaono-Sapolu's converted try and an exchange of penalties sent the Cherry and Whites in at half-time 17-13 ahead.
Tuilagi then cut loose for his treble, going over for his second with a Chris Ashton-style swallow dive.
But Gloucester refused to lie down, a superb Matt Cox pass putting fellow back-row colleague Hazell in, before Molenaar's touchdown and Burns' conversion brought the scores level at 34-34.
When Tigers' Thomas Waldrom stormed clear to send over Twelvetrees, it looked like Leicester would win.
However, with four seconds left, Fuimaono-Sapolu intercepted Jeremy Staunton's pass 60 metres out to sprint over, Burns converting with the last kick of the game.
Gloucester assistant coach Carl Hogg told BBC Radio Gloucestershire:
"This was a rollercoaster of a game. The effort and the desire that was shown within the 80 minutes was outstanding. We got themselves off to an excellent start in the first 20 minutes.
"We just hung in there, we made a few mistakes defensively, but our work ethic was outstanding and that's something that may have been lacking in the last week or two and it was certainly back today.
"We gave away two soft tries just after half time and you do wonder have we got the resilience to bounce back - particularly at a place like Welford Road - but I say we showed bag loads of character today. I'm very pleased for the players."
Leicester coach Richard Cockerill:
"There were that many mistakes and loose passes, I don't know whether some of the players thought it was a testimonial match.
"We have got to be better than that. We set our standards high, and that wasn't good enough. Next week will be an uncomfortable week for some.
"At 14 points clear, we made mistakes and let them run through us, and we ended up conceding five tries."
Leicester: Hamilton; Agulla, M Tuilagi, Twelvetrees, A Tuilagi; Flood, Youngs; Stankovich, Hawkins, Castrogiovanni; Mafi, Skivington, Croft, Woods, Waldrom.
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.