29 cases of femoral mononeuropathy are reported. While the clinical features of the femoral neuropathy are easily identified, the etiology is often hard to establish. The cases reported tend to fall into three general categories: 1) cases without major diagnostic difficulties (e.g. diabetic neuropathy); 2) those in which the definite diagnosis results from combined evidence of laboratory and instrumental data (degenerative changes in the lumbar spine, compressions, entrapments, etc.); 3) those in which the negative result of the investigations prevents a positive diagnosis and hence a presumptive etiology (spondylosis, inflammatory process, ischemia of the nerve) may be formulated. Attention is drawn to the favorable course of the condition in the patients of this group.