The scent‐marking behaviour of a group of six saddle‐back tamarins,Saguinus fuscicollis nigrifrons, was studied in the Amazon rain forest of north‐eastern Peru. Three types of scent marking were recognized: anogenital marking, suprapubic marking and sternal marking. Anogenital marking was the most frequent type. Two or more scent‐marking acts of the same or different type were generally combined into sequences. Most scent‐marking was performed on branches and lianas; trunks were infrequently used. The tamarins mainly marked on horizontal or inclined substrata with diameters between 3 and 10 cm and a height between I and 10 m. The temporal distribution of scent‐marking exhibited a maximum in the early morning between 06:00 and 07:00h and a minimum between 16:00 and 17:00h. The majority of scent‐marking occurred in the peripheral areas of the home‐range. The spatial distribution of scent‐marking was correlated with the intensity of home‐range use. No elevated frequencies of scent‐marking were observed during intergroup encounters. The results of this field study are compared with findings from laboratory studies, and hypotheses concerning the function of scent