Regional distribution of glycoconjugates in normal and neoplastic colonic mucosa was studied by means of eight lectins: Dolichos biflorus (DBA), Glycine max (SBA), Triticum vulgare (WGA), Arachis hypogaea (PNA), Griffonia simplicifolia-I (GS-I), Canavalia ensiformis (Con A), Limax flavus (LFA), and Ulex europaeus-I (UEA-I). The lectin binding patterns were examined in 40 normal colonic mucosa (NM) (12 proximal (P) and 28 distal (D], 38 carcinomas (15 P and 23 D), and 31 transitional mucosa (TM) (9 P and 22 D). Sections of NM located 5 cm and 10 cm distant from the tumour and sections from the resection margins (more than 10 cm from the tumour) of the surgical specimens were also studied in 19 cases (6 P and 13 D). In NM, regional differences between the proximal and distal colon were detected with most lectins. DBA, SBA and LFA bound mainly to the goblet cell mucin of the distal colon, while GS-I and UEA-I labelling predominated in proximal colonic mucosa. The lectin reactivity in carcinomas was: DBA 26%, SBA 63%, PNA 95%, GS-I 66%, UEA-I 76%, WGA 100%, Con A 92% and LFA 42%. No regional differences were observed in the lectin patterns of proximal and distal colonic carcinomas nor was any relationship detected between lectin reactivities and Dukes stage, size or histological type of tumours. Transitional mucosa of both the proximal and distal colon showed an increase in PNA-binding and loss of DBA and SBA. LFA and UEA-I reactivity in proximal TM was similar to that observed in proximal NM. Distal TM showed a decrease in LFA labelling and the appearance of UEA-I reactivity in goblet cell mucin in 5 cases (23%). The reactivity of the other lectins was as with NM. The only change in normal mucosa distant from tumours was a focal increase in PNA reactivity in 4 cases. These findings suggest that carcinomas from different colonic regions have a more uniform distribution of carbohydrates than the respective NM.