Neath claimed the scalp of Llanelli with a 25-7 victory at the Gnoll.
The home side outscored their opponents by three tries to one to move up to third place in the Welsh Premiership.
It was Llanelli's third defeat in six Premiership games, their grip on the title seemingly loosening.
Neath scored tries via Steve Tandy, Shaun Connor and Shane Williams. Conner added eight points thanks to two conversions and two penalty goals.
Llanelli's try came from third string scrum-half Robert Walters - who made the most of his chance with Dwayne Peel and Guy Easterby away on Test duty. Fullback Barry Davies converted
Tries: Tandy, Connor, S Williams
Cons: Connor 2
Pens: Connor 2
Con: B Davies
Caerphilly put one over valleys rivals Ebbw Vale with a narrow 31-28 victoryat a bitterly cold Virginia Park.
Tauna'holo Taufahema bagged a brace Roddy Boobyer and Ryan Howell weighed in with fine tries.
Justin Thomas converted all four five-pointers, and added a penalty goal to secure the home win.
Ebbw Vale made a match of it, scoring three tries. Richard Davies, Mark Meenan and Damien Pensini all crossed for the visitors.
Despite Bryan Shelbourne contributing 13 points via three penalty goals and two conversions, the Castletown men held on for their first Welsh Premiership win of the season.
However, they still remain rooted to the foot of the table.
Tries: Taufahema 2, R Boobyer, Howell
Cons: Thomas 4
Tries: Davies, Meenan, Pensini
Cons: Shelbourne 2
Pens: Shelbourne 3