The effect of cold-working on hydrogen solubilities in the dilute region (a phase) has been investigated for Pd, -,Ni,(xs 0.2), Pd, -,Pt,(xsO.l9), and Pd, _,Ni(,,,),Ag(,,,),(xs0.2) alloys by measuring pressure-composition isotherms between 273 and 348 K. The enhancement of hydrogen solubility in Pd-Ni alloys resulting from dislocation-hydrogen interaction tends to increase with increasing Ni content, in contrast to the case of Pd-Ag and Pd-Au alloys. On the other hand, the solubility enhancements in Pd-Pt and Pd-NiAg alloys did not change significantly with alloying metal contents. These results can be qualitatively explained by the interactions between the alloying elements with different sizes and the stress fields of dislocations. The hydrogen trapping at defects such as vacancies was also predicted from the observation of the initial region of the isotherms for coldworked alloys. It was found that the extent of pressure hysteresis in the isotherm for Pdo,,Nio,, alloy which has been initially cold-worked is less than for the well-annealed alloy and in the case of Pdo~3Ni~~0,5Ag0,075 alloy the hysteresis disappears completely.