B737-300 RECEIVED AN ERRONEOUS GPWS TERRAIN WARNING AND CLBED PER COMPANY PROCS. THERE WAS MD80 TFC ABOVE THEM AND ATC WAS CONCERNED ABOUT A POTENTIAL CONFLICT. NO TCASII WARNING RECEIVED. GPWS PERFORMANCE WAS WRITTEN UP IN THE LOGBOOK.

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INBOUND TO LAS ON THE CRESSO ARR. WE WERE GIVEN A VECTOR OFF OF THE ARR AND A DSCNT TO 6100 FT MSL IN PREPARATION FOR A L BASE ENTRY TO A VISUAL APCH TO RWY 25L. WHILE IN LEVEL FLT AT 6100 FT MSL; WE RECEIVED A GPWS TERRAIN WARNING. IN COMPLIANCE WITH OUR COMPANY PROCS; I INSTRUCTED THE FO TO INCREASE PWR AND CLB. WE LEVELED AT 6800 FT MSL AFTER THE TERRAIN WARNING WAS SILENCED. LAS APCH CTL WAS CONCERNED ABOUT MD80 TFC IN A L DOWNWIND ABOVE US APCHING FROM OUR 9 O'CLOCK POS. AFTER INSTRUCTING THE FO TO CLB; I INFORMED LAS APCH OF THE GPWS WARNING AND CLB. I MAINTAINED VISUAL CONTACT WITH THE MD80 THROUGHOUT THE ENTIRE MANEUVER. WE WERE SUBSEQUENTLY CLRED FOR A VISUAL APCH. IN A PHONE CONVERSATION WITH THE APCH CTL SUPVR; HE SAID THERE WAS NOT A SEPARATION CONFLICT WITH THE MD80 BUT THAT HE WAS CONCERNED ABOUT THE POTENTIAL FOR ONE. HE WAS ALSO SURPRISED THAT WE RECEIVED A GPWS WARNING SINCE THEY VECTOR NUMEROUS ACFT OVER THE TERRAIN IN THAT AREA AT 6100 FT MSL. I ALSO EXPLAINED THAT OUR COMPANY PROCS REQUIRE AN IMMEDIATE CLB UPON RECEIVING A GPWS TERRAIN WARNING AT NIGHT OR IN IMC WHEN THE TERRAIN IS NOT IN SIGHT. AFTER TALKING TO OUR MAINT CTL; I WROTE A MAINT DISCREPANCY ON THE GPWS TO HAVE THE SYS CHKED FOR PROPER OP. SINCE WE WERE AT THE MVA OF 6100 FT MSL; I FEEL THAT WE WERE GIVEN AN INCORRECT TERRAIN WARNING.