Saliva and 24-h urine samples were collected from male Schistosomiasis (bilharzia) patients with S. haematobium infection and possible concurrent S. mansoni infection without diagnosed bladder cancer (n = 27), bilharzia patients with diagnosed bladder cancer (n = 23) as well as a comparative control group (n = 27) of healthy Egyptian volunteers with no current bilharzia infection and/or bacterial urinary tract infections from the Nile Delta area of Egypt. Saliva samples were analysed for the presence of nitrate and nitrite; urine samples were analysed for the presence of nitrate, nitrite, volatile and non-volatile N-nitroso compounds. Bilharzia patients prior to, and after, diagnosed bladder cancer regularly excreted free nitrite as well as volatile nitrosamines (N-nitrosodimethylamine, N-nitrosodiethylamine, N-nitrosopiperidine and N-nitrosopyrrolidine) in addition to which elevated concentrations of non-volatile N-nitrosamino acids (N-nitrosoproline, N-nitrososarcosine, N-nitrosothiazolidine-4-carboxylic acid and its 2-methyl derivative) were also present. Total urinary excretion of volatile N-nitroso compounds (0.32 +/- 0.64 micrograms/day; mean +/- SD) and non-volatile N-nitroso compounds (31.20 +/- 22.07 micrograms/day) was observed in the Egyptian control group. Significantly higher concentrations were found in bilharzia patients: 3.47 +/- 6.42 (P less than 0.05) and 62.91 +/- 21.96 (P less than 0.05); as well as in bilharzia patients with diagnosed bladder cancer: 1.71 +/- 1.96 (P less than 0.02) and 44.94 +/- 7.31 respectively. Free nitrite was found in the urine of two volunteers in the Egyptian control group (1.7 and 3.0 micrograms/day), urinary nitrite was significantly increased in bilharzia patients (5.18 +/- 9.11 micrograms/day, P less than 0.02) and in bladder cancer patients (1.75 +/- 2.81 micrograms/day, P less than 0.05). Nitrate concentrations were elevated from 139.3 +/- 82.2 in the control group to 143.6 +/- 136.3 and 175 +/- 190 in the bilharzia and bladder cancer groups respectively. These results indicate that significant in vivo formation of nitrite and volatile N-nitroso compounds occurs in the urinary bladder of bilharzia patients and this may be an oetiological factor in the induction of bilharzial bladder cancer associated with S. haematobium infection.