Abstract: This invention relates to treatment or prevention of nephrotic syndromes by administration of a derivative of the fluoroquinolone class corresponding to the general formula: ##STR1## in which: R.sub.1 is an alkyl (1 to 4 carbon atoms), fluoroethyl, cyclopropyl, methylamino or difluorophenyl radical, X represents a nitrogen atom or a group .dbd.CRT.sub.7 -- in which R.sub.7 is H, Cl or F or alternatively R.sub.7 forms, with the R.sub.1 radical and the atoms to which they are attached, a six-membered heterocycle substituted by methyl and optionally containing an oxygen or sulphur atom, R.sub.2 is H, or can represent an amino radical, if R.sub.7 is F, and R.sub.3 is H, a 2,8-diazabicyclo[4.3.0]non-8-yl radical or a radical of structure: ##STR2## in which R.sub.4, R.sub.5 and R.sub.6 are identical or different and represent H or methyl, or one of its pharmaceutically acceptable salts.