The host range of human immunodeficiency virus (HIV) is quite narrow. Therefore, analyzing HIV-1 pathogenesis in vivo has been limited owing to lack of appropriate animal model systems. To overcome this, chimeric simian and human immunodeficiency viruses (SHIVs) that encode HIV-1 Env and are infectious to macaques have been developed and used to investigate the pathogenicity of HIV-1 in vivo. So far, we have many SHIV strains that show different pathogenesis in macaque experiments. However, dynamic aspects of SHIV infection have not been well understood. To fully understand the dynamic properties of SHIVs, we focused on two representative strains — the highly pathogenic SHIV, SHIV-KS661, and the less pathogenic SHIV, SHIV-#64 — and measured the time-course of experimental data in cell culture and rhesus macaque and analyzed them. I would like to discuss our quantitative results and future direction of this study.