The problem of step-flow crystal growth is considered for the specific case of the {110} face of \ensuremath{\alpha}-${\mathrm{HgI}}_{2}$. It is shown that the step-flow growth is inhibited by adsorption and high coverage factor ranging from 0.2 to 0.3. The time for full coverage of the adlayer is the same order of magnitude as the adsorption time, and influences therefore the characteristic time of the step-flow problem, relevant diffusion length, and step-flow velocity. Step-flow growth proceeds under kinetic/diffusion or diffusion control. The case of kinetic/diffusion control should reveal itself in the rectangular form of screw dislocation growth spirals with rounded sides and corners (the extent of corner rounding should correspond to characteristic diffusion length, \ensuremath{\simeq}1-3 \ensuremath{\mu}m), while the case of diffusion control should reveal itself in the circular form of dislocation spirals. Suggested values of the adsorption energy ${\mathit{E}}_{\mathit{a}}$\ensuremath{\simeq}(0.55-0.6)\ensuremath{\Delta}H\ensuremath{\simeq}0.63-0.69 eV (with steric factor within the range of S=1-0.3, respectively) and activation energy of incorporation into steps \ensuremath{\simeq}0.3-0.35 eV give a good agreement of the growth rates obtained within the framework of the step-flow model considered with three different sets of experimental data [T. Kobayashi et al., J. Electrochem. Soc. 130, 1183 (1983); M. Isshiki et al., J. Cryst. Growth 102, 344 (1990); M. Zha et al., ibid. 115, 43 (1991)]. \textcopyright{} 1996 The American Physical Society.