Purpose: The goal of this study was to compare the in vitro bioactivity in simulated body fluid (SBF) of commercially available dental implants. Materials and Methods: Bioactivity, according to ISO 23317, of commercially available dental implants with various surface modifications (BIO-surface, SLA, SLActive, TiUnite, and OsseoSpeed) was tested in SBF for 1 and 3 weeks. Surface characterizations, especially calcium and phosphorus surface content before and after the immersion in SBF, were performed. The effect of surface treatment on bioactivity was studied. Results: Differences between surfaces before immersion in SBF were confirmed by Raman spectroscopy, x-ray photoelectron spectroscopy (XPS), energy-dispersive x-ray spectroscopy (EDX), and scanning electron microscope (SEM) analysis. Calcium and phosphorus surface content was increasing within the tested period in the case of two (BIO-surface and SLActive) of the five tested dental implants. Calcium-phosphate precipitation was observed by SEM, XPS, EDX, and x-ray micro‑diffraction (μ-XRD) analysis. Conclusion: Two (BIO-surface from LASAK and SLActive from Straumann) of the five tested dental implants were found to be bioactive, according to ISO 23317. Although it is difficult to unambiguously determine the properties that have influence on the hydroxyapatite precipitation rate, multiple properties that the two surfaces have in common were found. Keywords: dental implant, in vitro bioactivity, ISO 23317, SBF, surface treatment