The sodium salt of melamine-phenol formaldehyde sulfonate (MPhFS), melamine formaldehyde sulfonate (MFS), and phenol formaldehyde sulfonate (PhFS) were prepared according to a four-step reaction procedure. The four steps of the reaction are hydroxymethylation, sulfonation, low pH condensation, and high pH rearrangement. Fourier transform IR and differential scanning calorimetry spectra were used to determine the structure of the synthesized resins. The effects of MFS, PhFS, MPhFS, and commercial superplasticizers on the rheological properties of cement pastes were investigated using a rotating coaxial viscometer. It was found that the prepared resins enhanced the rheological properties of cement pastes more than commercial ones. (C) 2003 Wiley Periodicals, Inc.