I studied the breeding biology of the Crested Gallito (Rhinocrypta lanceolata) in the Reserve of Ñacuñán (western Argentina) from September 1995 to January 1999. The laying period extended from mid-September to late January, a month longer than previous reports from Argentina. The closed nest was globular with a side entrance and was made primarily of grasses. In Ñacuñán, this species preferred to nest in atamisque (Capparis atamisquea). Atamisques selected for nesting were 1.6–3.5 m in height, and nests were 1.0–2.1 m above the ground. Mean clutch size (2.2 eggs) did not show a year or a seasonal variation. Mean egg size and mass were less than those reported previously. The incubation period lasted 16–17 d and the nestling period 14–15 d. Eggs hatched asynchronously. No cases of brood parasitism by Shiny Cowbird (Molothrus bonariensis) were observed.