AbstractQuantitative methods are presented for distinguishing rheologically‐important thiol and disulphide groups of wheat dough from those which are unimportant. The determinations are carried out in the farinograph and the use of extracting solvents is completely avoided. Dithiothreitol andN‐ethylmaleimide are used as respective titrants of disulphide and thiol groups.Less than 4% of the total disulphide is involved in determining development time; 11 to 13% is involved in the resistance to mixing. About 25 to 35% of the total thiol is involved in both development and tolerance to mixing. A positive relationship between the content of rheologically‐important disulphide and development time has been shown in flours from several varieties of wheat.It was further found that the addition of iodate can rapidly increase the resistance to mixing of a partly reduced dough.The nature of the rheologically‐important thiol and disulphide groups is discussed in relation to current knowledge of their distribution among large and small molecules, their importance in maintaining structure and their involvement in thiol‐disulphide exchange reactions duri