During cell division, a functional, bipolar mitotic spindle is essential for the faithful segregation of chromosomes into daughter cells. Each spindle pole is organized by a centrosome, a microtubule-organizing structure that contains a pair of centrioles surrounded by a proteinaceous matrix called the pericentriolar material. Centrosomes contain numerous uncharacterized proteins, many of which are likely to be involved in the regulation of centrosome duplication during the S phase of the cell cycle. Here (p. 3039), Jens Lüders and colleagues analyze the function of the previously uncharacterized protein SPICE (spindle and centriole protein; also known as CCDC52). The authors show that SPICE is associated with spindle microtubules during mitosis and with centrioles throughout the cell cycle. RNAi depletion of SPICE in human cells, they report, impairs centriole duplication and disrupts mitotic-spindle architecture, spindle-pole integrity and chromosome congression. Occasionally, these severe mitotic defects occur even in cells in which centriole duplication has proceeded normally. The authors propose, therefore, that SPICE is a dual-function regulator that is required for centriole duplication and for the formation of a functional bipolar mitotic spindle.