Photographys of Mars obtained during the 1986 opposition of the planet have been used to derive the regression curve for the south polar cap between Ls=190¿ and Ls=255¿. The 1986 regression appears to have been unexceptional until after Ls=230¿, when it becomes retarded relative to the normal established by the 1971 and 1977 regressions. A study of the data as a function of the filter used suggests that circumpolar clouds were present in early spring, unlike the case in the 1977 recession. ¿ American Geophysical Union 1990