Abstract: A segmented spiral staircase and kit for its construction has a plurality of laterally extending step segments. Each step segment has a step surface with an inboard, donut-shaped end section and lower downwardly extending support members. Each step segment also has an upstanding baluster rail member connected by screws to the outboard end of the step surface. The step segments are each rotatably mounted, at their respective inboard end sections, in offset fashion through a vertically standing support post. The baluster rail members of the step segments are configured to be aligned adjacent to each other and are connected one to the other by screws. Spacer sleeves separate each of the step segments, whose lower support members are positioned against the vertical surfaces of the sleeves. Alternate stacking of the sleeves and step segments and connection of the baluster rail members produces a sturdy staircase structure which also includes an upper landing member.