Introduction: while modularity that permits independent fitting of the diaphysis, metaphysis, length, offset, and version may greatly facilitate reconstruction and ultimate clinical performance, potential generation of metallic wear debris due to fretting at the modular interface is a concern. Materials and methods: serum titanium was analyzed using inductively coupled plasma sector field mass spectrometry. titanium levels were analyzed preoperatively and at 1-year follow-up in patients treated with the acumatch^? m-series prosthesis, which has a three-piece modular femoral stem and preopera-tively, at 1-year and 2-year follow-up in patients treated with the versys nonmodular femoral stem. Results: Pre-operative mean serum titanium levels were not significantly different in patients receiving the modular Acumatch (0.25 ppb) or the nonmodular Versys (0.21 ppb) femoral stems. Titanium level in the Acumatch group was significantly higher at 1 year (2.56 ppb; range: 0.65–5.62) than those obtained for the Versys group at 1 year (1.86 ppb: range: 1.08–2.65) or 2 year (1.46 ppb: range: 1.12–2.02) post-operatively (P< 0.05). Titanium levels were significantly increased at each follow-up in both the Acumatch and Versys groups when compared to pre-operative levels (P< 0.001). Discussion/ Conclusion: Serum titanium levels were significantly increased in patients treated with the highly modular Acumatch hip prosthesis when compared to patients treated with the nonmodular Versys femoral stem. The clinical relevance of this finding is currently unknown.