We describe the first steps in developing an OMERACT magnetic resonance imaging (MRI) scoring system for peripheral psoriatic arthritis (PsA). A preexisting MRI dataset (finger joints) from 10 patients with PsA was scored by 4 readers for bone erosion, bone edema, synovitis, tendinopathy, and extracapsular features of inflammation (including enthesitis) according to specified criteria. Scoring reliability between readers was moderate to high for bone edema and erosion, but lower for soft tissue inflammation. Measures to improve reliability for future exercises will include reviewing definitions of pathological features and prior reader calibration.