The low-mass X-ray binary and Z source GX 17+2 undergoes infrared K-band brightening episodes of at least 3.5 mag. The source of these episodes is not known. Prior published K-band magnitudes and new K-band measurements acquired between 2006 and 2008 suggest that the episodes last at least 4 hr and have a period of 3.01254 ± 0.00002 days. Future bright episodes can be predicted using the ephemeris JD_(max)(n) = 2454550.79829 + (3.01254 ± 0.00002)(n) days. A growing body of evidence suggests that the GX 17+2 could have a synchrotron jet, which could cause this activity.
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