A solid base catalyst was obtained through attachment of tetramethylguanidine onto silica gel surface. Infrared spectroscopy, C-13 and Si-29 nuclear magnetic resonance data are in agreement with the proposed structure. SEM images showed that the catalyst presented high homogeneous spherical particles of 1 mu m with surface area of 216.14 +/- 34 m(2) g(-1). The obtained material was used as catalyst in the transesterification of soybean oil for biodiesel production. The catalytic efficiency was followed and the biodiesel conversion presented a yield of 86.73 +/- 2.2% at 3 h of reaction. The catalyst was recovered and reused nine times, maintaining about 62% of its catalytic efficiency. (c) 2008 Elsevier B.V. All rights reserved.