With the progressive improvement in the survival with acute lymphocytic leukemia (ALL), the side effect of therapy becomes a more significant problem. In this paper, a case of the pyogenic osteomyelitis of the spine after therapy for ALL was reported. He was 58 years old. He suffered from ALL for 1 year and 4 months before the onset of low back pain. After 1 month of the onset of low back pain, the roentgenogram showed the irregularity of the end-plate (L4/5). We suspected the pyogenic osteomyelitis of the spine. So we started injection of antibotiics, then low back pain was decreased with a drop in CRP. But he died of pneumonia after 1 year and 8 months of the therapy for ALL. From the autopsy, we observed the disappearance of the endplate, and the formation of granulation with lymphocytes and plasm cells at the disc (L4/5). And the lymphocytic blast cells were observed at the L4 and L5 vertebra.