C172 pilot reported near midair collision in the traffic pattern.

Attributes
ACN	1036857
Time
Date	201209
Local Time Of Day	0601-1200
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	Skyhawk 172/Cutlass 172
Operating Under FAR Part	Part 91
Flight Phase	Initial Approach
Route In Use	None
Flight Plan	None
Person 1
Function	Pilot Flying Single Pilot
Qualification	Flight Crew Flight Instructor Flight Crew Instrument Flight Crew Multiengine
Experience	Flight Crew Total 1050
Events
Anomaly	Conflict NMAC
Miss Distance	Horizontal 100 Vertical 75

Narrative:

ATC was congested and confusing. Four [light aircraft] trying to approach runway. Aircraft flying from left base came up below and behind me while established on 4 mile final. Not having the traffic behind me in sight I advised 'negative contact'; ATC advised right 360 and as I looked right another aircraft came out from behind and was crossing my flight path. I immediately pulled up and banked away to avoid the traffic. He continued inbound. I flew safely away and followed.

Original NASA ASRS Text

Title: C172 pilot reported NMAC in the traffic pattern.

Narrative: ATC was congested and confusing. Four [light aircraft] trying to approach runway. Aircraft flying from left base came up below and behind me while established on 4 mile final. Not having the traffic behind me in sight I advised 'negative contact'; ATC advised right 360 and as I looked right another aircraft came out from behind and was crossing my flight path. I immediately pulled up and banked away to avoid the traffic. He continued inbound. I flew safely away and followed.

Data retrieved from NASA's ASRS site as of July 2013 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.