In this study, we assessed the effectiveness of inflammatory markers to diagnose and monitor the treatment of osteomyelitis in the diabetic foot. We evaluated 35 consecutive patients admitted to our hospital with infected foot ulcers. Patients were divided in two groups based on the results of bone culture and histopathology: osteomyelitis and no osteomyelitis. The erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), procalcitonin (PCT), interleukin-6 (IL-6), interleukin-8 (IL-8), tumor necrosis factor alpha (TNFα), monocyte chemotactic protein-1 (MCP-1) and macrophage inflammatory protein-1 alpha (MIP1α) were measured at baseline after 3 and 6 weeks of standard therapy. PCT levels in the osteomyelitis group were significantly higher at baseline than in the group with no osteomyelitis (P = 0·049). There were no significant differences between the two groups in the levels of the other markers. CRP, ESR, PCT and IL-6 levels significantly declined in the group with osteomyelitis after starting therapy, while MCP-1 increased (P = 0·002). TNFα and MIP1α levels were below range in 80 out of 97 samples and therefore not reported. Our results suggest that PCT might be useful to distinguish osteomyelitis in infected foot ulcers. CRP, ESR, PCT and IL-6 are valuable when monitoring the effect of therapy.