Our understanding of the clinical entities known as the Chiari -malformations has tremendously increased over the past 40 years. We have moved from a position of grouping the CIM and syringomyelia patient in the degenerative category to a fundamental understanding of the pathophysiology. This has led to surgical intervention that has generally favorable outcomes. Our understanding that patients with the Chiari II malformation must have adequate CSF diversion is of paramount importance. Additional patients with complex issues of ventral compression and micromovement at the craniocervical junction challenge even the experienced neurosurgeon. However, the understanding of few diseases has progressed so far in such a short time.