Wall siding for installation on the walls of a structure comprising a plurality of panels, each comprising a nailing hem, a flange member, upper and lower declinations being substantially planar and extending downwardly and slightly outwardly from the nailing hem, and a downwardly opening U-shaped channel formed between and interconnecting the flange member and the upper declination. Upper and lower shoulders extend inwardly and substantially horizontally from lower edges of the upper and lower shoulders, respectively. A lip extends upwardly and curves slightly outwardly from an innermost edge of the lower shoulder. An inverted U-shaped projection extends substantially along the length of the upper shoulder and a slot extends from a vertical edge of the siding panel along a portion of the upper shoulder. When installed, the lip of a siding panel mates with and engages the U-shaped channel of a vertically adjacent panel in a male-female relationship, and the projection of a siding panel mates with and engages the slot of a horizontally adjacent panel in a male-female relationship. Siding panels having more than two declinations are also disclosed.