Diamino-diphenyl-ureas may be obtained by the condensation of a diaminobenzene, in which the amino groups are not in the ortho position to each other, with urea in an aqueous medium at a raised temperature. Suitable diamino benzenes are 1-methyl-2 : 4-diaminobenzene, 1-methoxy-2 : 4-diamino-benzene, 1 : 4-diamino-2-chlorobenzene, 1 : 4-diaminobenzene - 2 - carboxylic acid, 1 : 4-diaminobenzene-2-sulphonic acid and especially 1 : 4- and 1 : 3-diaminobenzene. When the diaminobenzene is metaphenylene diamine it is desirable to conduct the reaction in the presence of an acid binding agent, preferably in the presence of 4 equivalents of sulphuric acid. In examples: (1) paraphenylene diamine is heated with urea in water to give 4 : 41-diamino-diphenyl-urea, a dichlorinated 4 : 41-diamino-diphenyl-urea, may be obtained in an analogous manner from 1 : 4-diamino-2-chlorobenzene and urea and (2) meta-phenylene diamine and urea are heated in aqueous sulphuric acid to give 3 : 31-diamino-diphenyl-urea. Specification 254,667, [Class 2 (iii)], is referred to.