Abstract: A lift arm lock down apparatus for a load lifting vehicle is described. The vehicle has a vehicle body and a lift arm or boom rotatable between a raised and a lowered position about a horizontal pivot on the vehicle body. The lift arm lock down apparatus includes a lock having first and second cooperating lock members for selectively locking the lift arm to the vehicle body in the lowered position. The lock members are respectively mounted on the lift arm and the vehicle body. At least one lock member is movable by an appropriate manually or automatically operated mechanism between an unlocked position permitting tilting of the lift arm and a locked position where the lock members are releasably interconnected when the lift arm is at the lowered position. The lift arm lock down apparatus prevents accidental lifting of the lift arm, when the operator is entering or exiting the operator's compartment and may be used as a theft deterrent when the lift arm is locked in a lowered, ground engaging position.