AbstractGC‐olfactometry (GC‐O) refers to the use of human assessors as a sensitive and selective detector for odour‐active compounds. The aim of this technique is to determine the odour activity of volatile compounds in a sample extract, and assign a relative importance to each compound. Methods can be classified into three types: detection frequency, dilution to threshold and direct intensity. Dilution to threshold methods measure the potency of odour‐active compounds by using a series of extract dilutions, whereas detection frequency and direct‐intensity methods measure odour‐active compound intensity, or relative importance, in a single concentrated extract. Factors that should be considered to improve the value of GC‐O analysis are the extraction method, GC instrument conditions, including the design and operation of the odour port, methods of recording GC‐O data and controlling the potential for human assessor bias using experimental design and a trained panel. Considerable emphasis is placed on the requirement for multidimensional GC analysis, and on best practice when using human assessors.