Background: Baastrup's disease or "kissing spines syndrome" was first described in 1933 as a cause of postural back pain, which was thought to be related to the adjacent 'kissing' of the spinous processes. The diagnosis was based on 'symptoms' of positional back pain with extension, and plain radiographs showing close approximation of the spinous processes. The aim: Baastrup’s disease is overwhelmingly underdiagnosed and often missed due to a lack of knowledge and/or improper diagnostic techniques, leading to frequent mistreatment. A case of Baastrup’s disease is reported. Case report: 70-year-old patient, with a 4 years history of back pain presented a severe neurogenic claudication for a year. Neurological evaluation was normal. Extension of the lumbar spine exaggerates the pain. Locally the pressure of the spinous processes shows a painful point located next to L4-L5. Lumbar CT scan showed a typic “kissing posterior spinous processes” associated with disc space narrowing at multiple levels especially L4-5 and L5-S1. The patient underwent a decompressive laminectomy. A neoarticulation with synovial structure was noted, between L4 and L5 spinous process. Postoperative was unremarkable with good results after two months physiotherapy program. Conclusion: Baastrup´s syndrome is more common in the lumbar spine with L4-L5 being the most affected region. Baastrup's disease is a part of dynamic degenerative process. Management must be adapted to clinical and radiological findings. Medical treatment can be conservative or surgical and an accurate diagnosis of the disease is necessary for determining appropriate treatment. If the predominant symptoms are related to neurogenic claudication or radiculopathy, surgical decompression or stabilization may be necessary.