Small-angle neutron scattering (SANS) and light scattering studies were carried out on an organogel consisting of a gelator, coded P-1, and dimethyl sulfoxide (DMSO). The gelator was made of an oligosiloxane stem and about eight branches of an amino acid derivative combined with a long alkyl chain. The amino acid part, N-n-pentanoyl-L-isoleucylaminooctadecane, was responsible for intermolecular association via hydrogen bonding between amide groups. After the complete dissolution of P-1 in DMSO at 85 degreesC, the solution was cooled, and the variations of the scattered light intensity were monitored as a function of the temperature. The scattered intensity increased drastically at about 40 degreesC when the P-1 concentration (C) was 3.5 g/L, and this indicated gel formation. The SANS results showed that the scattering intensity function was a monotonically decreasing function, regardless of C. A master relationship of the scattering intensity was obtained with respect to C. These scattering studies disclosed the following facts. First, gelation could be monitored as an abrupt increase in the intensity. Second, the gel was composed of randomly oriented bundlelike clusters. Third, the structure factor could be reduced by the gelator concentration, and this indicated the presence of a self-similar structure across the gelation threshold. (C) 2004 Wiley Periodicals, Inc.