The observations reported were conducted in (1) 1984 and 1985 on the C. spinosa biotypes commonly cultivated on the islands of Salina and Pantelleria, and (2) in 1986 on a specialized caper plantation on the mainland of Sicily with the biotype Nocellara (from Pantelleria). Four biotypes (Ciavulara, Nocellara, Spinoso and Testa di lucertola) were distinguished on Pantellaria and 2 (Nocella and Spinosa) on Salina. Data are tabulated on stem length, number of nodes, number of capers, productivity index, lead dimensions, number of stamens, pistil length and average number of capers/10-node section of stem. Weekly stem development was recorded over 20 weeks. The best biotypes in commercial terms were Nocellara (no thorns) and Nocella (very small thorns); both were highly productive and yielded high quality capers. In trial (2), where Nocellara was propagated from cuttings, the results confirmed the high productivity and quality of this biotype, evident only 2 years after planting. The results indicated that a further improvement in quality might be obtained by regulating harvesting dates, taking into account the patterns of shoot growth and flower bud formation.