The clinical, radiologic, and operative findings, and clinical results in 26 cases of foraminal nerve root involvement, each treated by variable operative procedures for an existing pathologic condition, were studied. These 26 cases consisted of 8 intraforaminal or extraforaminal lumbar disc herniations and 18 foraminal nerve root entrapments. The cases with an extreme lateral lumbar disc herniation underwent lateral fenestration or osteoplastic hemilaminectomy without concomitant spinal fusion, and showed excellent operative results. A sufficient selective decompression was achieved with a good clinical result in the cases of lumbar spondylosis without preoperative spinal instability, by lateral fenestration or osteoplastic hemilaminectomy. This result suggests that the selective decompression procedure is recommended for cases with reliable preoperative diagnoses. When an intraspinal lesion makes it difficult to diagnose coexisting foraminal nerve root involvement, decompression of the nerve root canal, approaching from medial to lateral, is recommended. The fusion operation should be performed in cases undergoing even a unilateral total facetectomy, regardless of the patient's old age. A correct preoperative diagnosis is crucial in order to obtain satisfactory operative results.