B757 captain reported responding to a TCAS resolution advisory at FL340.

Attributes
ACN	1578432
Time
Date	201809
Environment
Flight Conditions	VMC
Aircraft 1
Make Model Name	B757 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	Cruise
Flight Plan	IFR
Person 1
Function	Captain Pilot Flying
Qualification	Flight Crew Instrument Flight Crew Air Transport Pilot (ATP) Flight Crew Multiengine
Experience	Flight Crew Last 90 Days 119 Flight Crew Total 15875 Flight Crew Type 991
Events
Anomaly	Conflict Airborne Conflict Deviation - Altitude Excursion From Assigned Altitude

Narrative:

While level at FL340; we received a TCAS TA; followed by a TCAS RA. The TCAS display showed a target approximately 100 feet above us (+01). We initiated a descent; at which time the RA resolved (went away). We had deviated less than 200 feet from our original altitude (down to approximately 33850 [feet]). We returned to FL340 and reported to ATC. They said they did not show any aircraft in the area.

Original NASA ASRS Text

Title: B757 Captain reported responding to a TCAS resolution advisory at FL340.

Narrative: While level at FL340; we received a TCAS TA; followed by a TCAS RA. The TCAS display showed a target approximately 100 feet above us (+01). We initiated a descent; at which time the RA resolved (went away). We had deviated less than 200 feet from our original altitude (down to approximately 33850 [feet]). We returned to FL340 and reported to ATC. They said they did not show any aircraft in the area.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.