This paper presents details of a monitoring program on a 40m-high nailed excavation in gneissic residual soil. Stability studies and stress-strain analysis of the nailed mass were fundamental for defining the most efficient and economical solution in terms of nails and excavation geometries. The nails are made of steel bars 25mm in diameter, placed in drill holes with variable lengths (15 to 24m), with vertical and in horizontal spacing of 2m. Instrumentation included inclinometer and tell-tales for monitoring horizontal displacements of the soil mass. Strain gauges were also placed on the steel bars for obtaining tension and bending along the nails. Design concepts and construction details are briefly described, together with details of the monitoring program and preliminary results.