A steel cord for reinforcing rubber articles comprises one wave-form or helical core steel filament and five to eight sheath steel filaments disposed around the core steel filament, the pitch Pc of the core steel filament is 3.0 dc/0.34.ltoreq.Pc.ltoreq.10.0 dc/0.34 (dc=diameter of steel core filament) and the core forming ratio Rc=Lc/dc (Lc is an amplitude of the wave or helix of the core steel filament) is within a particular range varying depending on the number of sheath steel filaments. A pneumatic tire contains a cross belt reinforced with the above-mentioned steel cords where (i) an angle .theta. formed by the reinforcing steel cords and the equatorial plane of the tire is: 12.degree..ltoreq..theta..ltoreq.30.degree. (ii) a gap between any two adjacent steel cords in the same layer of the cross belt, I, is: 0.5 mm.ltoreq.I.ltoreq.2.0 mm (iii) a gauge of the gum between any two facing steel cords in different layers of the cross belt, G, is: 0.35 mm.ltoreq.G.ltoreq.2.0 mm.