This paper presents some observations on the painting technique of Diego Velázquez and his materials, based on a study of six paintings in the Museo de Prado, Madrid. The paintings were studied at the Prado in May, 1980, at which time radiographs taken previously were examined and a new ridiograph of one of the paintings was taken. The paintings were also examined by infrared photography and reflectography. Microscopic study of a few of the paintings was possible, and a limited number of pigment samples and some cross-sections were taken for analysis.