# K033126: Monarch 21 Penile Plethysmograph System

- Pathway: 510(k) (Special)
- Applicant: Behavioral Technology, Inc.
- Decided: Oct 29, 2003 after 29 days
- Product code: LIL (Monitor, Penile Tumescence)
- Device class: U
- Recalls of this device: none
- Data: FDA decisions to Oct 25, 2026; recalls to Oct 12, 2026

## Lineage
Longest line of descent: 1 generation back to K936115 (1995). 1 ancestor in all.
1 later device descends from it; 1 cites it directly.
0 of 3 devices in its family (counting itself) have a Class I recall.

## Predicates on the family tree (from the FDA summary)
- K936115: Cat-600 Penile Plethysmograph, Farrall Instruments, Inc. (1995) Summary page 1.

## Most influential descendants
- K052929: Preftest Professional Suite (2006), 0 descendants of its own

## Indications for use
The MONARCH 21 system’s intended use is to measure sexual response to visual and auditory stimuli in male sexual offenders as an important part of evaluating individual treatment need and determining risk for recidivism.

Source page: https://510kreport.com/device/K033126
Methodology: https://510kreport.com/methodology