The aim of this study was to establish the concentration of insulin-like growth factor-I (IGF-I) in saliva of acromegalic patients, and to compare it with the basal levels of serum IGF-I and growth hormone. IGF-I was determined in extracted serum or neat saliva by a disequilibrium RIA using antibodies and iodinated ligand from Amersham and WHO 87/518 as standard. The detection limit of the assay was 0.5 microgram/l, and the intra- and interassay coefficients of variations were 7.9% and 15% respectively. Our study included 13 healthy adult individuals and 17 acromegalics. Compared with healthy adult subjects, acromegalics had significantly higher salivary IGF-I concentrations (mean +/- SEM 5.4 +/- 2.64 vs. 10.5 + -5.69 micrograms/l; p < 0.01), as well as serum IGF-I (176 +/- 42.9 vs. 520 +/- 98.8 micrograms/l; p < 0.0001) and somatotropin levels (1.2 +/- 1.02 vs. 15.4 +/- 9.89 micrograms/l; p < 0.0001). However, 47.1% patients (8 out of 17) with active acromegaly had salivary IGF-I concentrations within the normal range. Serum IGF-I and somatotropin concentrations were found to follow more closely the disease activity after adenomectomy, compared with the concentrations of salivary IGF-I. These results suggest that the IGF-I levels in serum and saliva are somatotropin-dependent. According to our results, measurement of IGF-I in saliva cannot be considered as an additional measure for evaluation of the disease activity in acromegaly, being less reliable than the determination of IGF-I and somatotropin in serum.