The regression of the Martian south polar cap during the 1988 apparition is examined with the measurements of the photographs of Mars obtained at the Bosscha Observatory, at the Hida Observatory, and the Kwasan Observatory. Around Ls=-230¿, the regression of the south polar cap in 1988 appears similar to those in other years. After Ls=240¿ the regression of the south polar cap in 1988 seems slower than those in 1956, in 1971, in 1973, or in 1977. However, in the period Ls=240¿--250¿, it seems faster than that in 1939 which is the slowest reported or than that in 1986 which is also very slow. The 1988 regression seems to be one of the slowest in the period Ls=240¿--290¿. Like the case of the south polar cap in 1986, the regression of the south polar cap in 1988 supports interannual difference of the regression of the south polar cap. The data from 1988 also support the proposition that the size of the south polar cap around Ls=250¿ becomes large in the year when global dust storms do not occur. ¿American Geophysical Union 1990