The boundedness of Calderón-Zygmund operators is proved in the scale of the mixed Lebesgue spaces. As a consequence, the boundedness of the bilinear null forms Qij(u, v) = ∂iu∂jv - ∂ju∂iv, Q0(u, v) = u tvt - ∇xu · ∇xv on various space-time mixed Sobolev-Lebesgue spaces is shown.
