Originated from the cross BR 83-147 x FT-Abyara, BRS 66 is indicated for seeding in the state of Rio Grande do Sul, Brazil. It was evaluated for grain yield and agronomic characteristics in multilocation trials from 1993/94 up to 1995/96 and showed a mean grain yield of 2,883 kg/ha. BRS 66 is resistant to soybean stem canker, brown stem rot, frog-eye leaf spot, race 1 of Phytophthora sojae, bacterial pustule and powdery mildew. This cultivar presents white flowers, brown pubescence, dull yellow seed tegument, brown hila, and determinate growth habit. Plant stature varies from medium to high, with good resistance to lodging. It shows a medium maturity cycle.