Infinite-dimensional non-abelian superalgebras, related to interacting massless higher-spin fields of all spins s ⩾ 3/2, are proposed. Conditions are formulated that provide uniqueness for these higher-spin superalgebras, denoted as shsρ(1) (ρ = 0 or 1). Among these conditions, the major role is played by the requirement that linearized curvatures of shsρ(1) coincide with the linearized higher-spin curvatures obtained previously. Subalgebras and contractions of shsρ(1) are considered. A higher-spin interaction, which is introduced in terms of the shsρ(1) curvatures, is discussed briefly. It is found that a gravitational interaction of massless higher spins requires non-analyticity in the cosmological constant.