Mono- and diquaternary salts of pyrimidylamino-cinnolines of trypanocidal activity are obtained from a pyrimidine substituted in the 2-, 4- (or 6-) position by amino- or lower alkylamino, by a halogen or thioether in another of these positions, and by, optionally, a lower alkyl, amino or lower alkylamino in the remaining one of these positions, and a cinnoline substituted in 4-position by amino, and optionally by further alkyl, either the pyrimidine compound or both being in the form of their quaternary salts, by heating the reagents together in presence of acid. The cinnoline compound may be employed in the form of a salt, or as a substance which will give rise to the amine under the conditions of reaction, such as an acyl derivative. In examples, pyrimidines substituted in the 4-position by chlorine, bromine or iodine, or by methylthio, in the 2-position by amino, methylamino, and isopropylamino, and in the 6-position by methyl, ethyl or amino, are made to react with 6-aminocinnolines, having in the 4-position, amino, acetylamino, methylamino, and a further methyl group, in the form of methiodide quaternary salt or a free amine. The pyrimidine compounds are used in the form of methiodide. The reaction takes place on heating with or without hydrochloric acid and the products are dimethiodides, methiodide - hydriodides, and monomethiodides or hydrates thereof, &c., and may be converted into other di- or mono-quaternary salts or hydrates by exchange or action of alkali. 4 : 6 - diamino - cinnoline 1 - methiodide is obtained by quaternating the 6-nitro-4-amino-cinnoline, followed by reducing with iron and hydrochloric acid, and the corresponding base by the reduction of 6-nitro-4-aminocinnoline. The base may be acetylated on the 6-amino group. The corresponding 6-amino-4-methyl-amino compound is obtained by the action of methylamine hydrochloride on 6-nitro-4-phenoxycinnoline, converting to the quaternary salt the 4-methylamino derivative obtained and reducing the product. The 6-amino-4-methyl-aminocinnoline base and the 3-methyl derivative are obtained by reduction of the 6-nitro compounds. 2 - Chloro - 4 - aminopyrimidine 1 - methiodide is obtained by quaternating the base. Specifications 634,471 and 663,096 are referred to.