Disclosed is a process for the treatment of gas containing mercaptans and acid gases, including the following steps: (1) separating the acid gases from the said gas and obtaining a sweetened gas and the flow of acid gases containing H.sub.2S; (2) reacting the H.sub.2S thus obtained in step (1) according to the Claus reaction; (3) concentrating the mercaptans in at least one cut of the said sweetened gas; (4) extracting the mercaptans of the said cut; and further comprising: (5) transforming the mercaptans into dialkyl-disulfide (DSO); (6) hydrogenating DSO into H.sub.2S; and (7) reacting the H.sub.2S thus obtained at step (6) according to the Claus reaction. An installation for carrying out this procedure is also described.