OBJECTIVE. The purpose of this study was to analyze the sonographic appearance of a large series of pathologically proven ganglia. MATERIALS AND METHODS . A computer search of sonography and pathology reports for hand and wrist ganglia was performed. All sonography reports and images were reviewed for ganglion size, location, presence of a neck, echogenicity, acoustic enhancement, locules, color Doppler flow, margins, wall thickness, and calcifications and to determine if the ganglion was palpable or collapsed. All pathology reports were reviewed for histologic features that were then correlated with the sonographic images. Ganglia were categorized into three groups: simple, complex cystic, and solid-appearing. RESULTS. Of 60 ganglia, 34 were complex, 91% of which were located within the dorsal or volar wrist; 97% had well-defined margins; 76%, locules; 68%, acoustic enhancement; 47%, a thick wall; 15%, internal reflectors; and 12%, blood flow. Of the 23 simple ganglia, 11 involved the extensor or flexor tendon sheath, 73% of which were simple. Complex ganglia had a larger mean volume than simple. Three ganglia were solid-appearing. A visible neck was seen in 25% of ganglia. CONCLUSION. Most ganglia are complex rather than simple on sonography. Complex ganglia are larger than simple ganglia; located within the dorsal or volar wrist; and usually have well-defined margins, thick walls, locules, and acoustic enhancement. A small percentage have blood flow and internal reflectors. Simple ganglia are smaller and can occur within the volar or dorsal wrist, or flexor tendon sheath. Most flexor tendon sheath ganglia are simple rather than complex. Solid-appearing ganglia, although unusual, may mimic a benign neoplasm or synovitis.