Two He-Ne-laser photometers were used to measure gravitational deposition of particles carried with laminar air flows through inclined circular tubes. If the magnitude of the projection of the settling velocity of aerosol particles in the direction of the air flow is small compared to the magnitude of the maximum velocity of the laminar air flow (rT sin β/L = ν sin β/u 0 ≪ 1), gravitational deposition for upward and downward flow can be described by DE = 2 π[2κ√(1 - κ 2 3) - κ 1 3 √(1 - κ 2 3) + arc sin κ 1 3], where κ = 3T cos β/4. The problem was applied to a system of randomly oriented circular tubes for which several analytical approximations were derived.