The determination of antimitotic activity of organic extracts from marine organisms generates expectations on the isolation of substances with potential anticancer activity. The antimitotic activity of crude organic extracts from 15 marine sponges from the Colombian Caribbean coast were tested in vitro against embryos of the sea urchin Lytechinus variegatus. 80% of the species evaluated (Spirastrella coccinea, Myrmekioderma rea, Iotrochota imminuta, Halichondria sp., Petromica ciocalyptoides, Cinachyrella kuekenthali, Biemna cribaria, Oceanapia peltata, Xestospongia proxima, Oceanapia bartschi, Polymastia tenax y Dragmacidon reticulata) showed significant levels of inhibiting activity on the mitotic divisions at the first cellular phase of fertilized eggs. The extracts from Halichondria sp., P. ciocalyptoides and Xestospongia proxima disintegrate the cellular nuclei instantly. Extracts from Cribrochalina infundibulum showed an intermediate level of activity, while extracts from Desmapsamma anchorata and Myrmekioderma gyroderma showed no activity.