Date: 201404
Local time of day: 1201-1800
Location: DEN.Airport, CO
Flight conditions: IMC
Weather elements / visibility: Windshear; 1
Light: Daylight
Aircraft: B737-700
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Initial Approach
Airspace: Class B DEN
ATC / advisory: TRACON D01
Reporter organization: Air Carrier
Reporter function: Pilot Not Flying; Captain
Human factors: Distraction; Physiological - Other; Confusion
Anomaly: ATC Issue All Types; Conflict Airborne Conflict
Detector: Automation Aircraft RA; Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Issued Advisory / Alert; Flight Crew Returned To Clearance; Flight Crew Took Evasive Action
Contributing factors: Airport; Weather
Primary problem: Ambiguous

Narrative: Event occurred on approximately a 12-mile final for the ILS 35R at DEN. I was the pilot not flying. The First Officer was the pilot flying. We were on the localizer 35R; 8;000 FT assigned altitude; 170 KTS assigned speed; and cleared for the ILS 35R approach. The localizer was captured/approach mode armed and the autopilot; and the autothrottles were engaged. We were below the glideslope.At this point; we received a TCAS Resolution Advisory to monitor Vertical Speed. We complied with this and maintained 8;000 FT. Looking at the MAP display; I noticed an aircraft 500 FT above us on TCAS that appeared to be conducting a simultaneous approach to [Runway] 35L. Shortly thereafter; we received a TCAS RA to descend. We complied with the RA and I notified Denver Tower that we were complying with a TCAS Resolution Advisory. We had to descend 300 FT to receive the Clear of Conflict notification from the TCAS system. I noticed that the aircraft that had been 500 FT above us was climbing and appeared to be executing a go-around. Denver Tower then contacted us and asked if we could continue the approach. I evaluated the situation and decided that it was safe to continue the approach. We were still on the 35R localizer; below the glideslope; well clear of any obstructions or terrain; and the aircraft was in a stable state. I asked the First Officer if he agreed with this decision and he did. I notified the Tower we would be able to continue the approach. The Controller then re-cleared us for the approach and landing. The remainder of the approach was made without further incident and we landed on [Runway] 35R. I subsequently notified Dispatch. I think we; as a crew; did a good job complying with the RA and used good CRM to determine the safest course of action following the RA.  I'm not sure what caused the RA as the aircraft 500 FT above us appeared to be maintaining altitude. That aircraft did appear laterally close; however. I don't know if separation was lost from an ATC perspective as the aircraft on [Runway] 35L was talking to a different Controller. It would be interesting to know if it was a pilot error; ATC error; or equipment malfunction. Regardless; we complied in accordance Company procedure.




Synopsis: A B737 on final for DEN Runway 35R received a TCAS RA DESCEND from traffic on Runway 35L; but continued the approach after descending 300 FT; leveling; then regaining the glideslope.