Within the framework of the post form distorted-wave Born-approximation theory of breakup reactions, we study the elastic and inelastic breakup of the $^{3}\mathrm{He}$ particle. With the standard set of parameters for the optical model potential we are able to understand coincidence and inclusive data for this process, which were recently measured by Matsuoka et al. at the incident $^{3}\mathrm{He}$ energy of 90.0 MeV. The elastic breakup accounts only for about 20% of the total inclusive ($^{3}\mathrm{He}$, $d$) yield. With our theory we are able to understand quantitatively the breakup process, a dominant peripheral reaction mechanism.NUCLEAR REACTIONS $A(^{3}\mathrm{He}, d)$ breakup at ${E}_{^{3}\mathrm{He}}=90.0$ MeV, $A=^{51}\mathrm{V}, ^{90}\mathrm{Zr}$; calculated elastic and inelastic breakup cross sections; post form DWBA theory of breakup.