During 1987-88, ten varieties of cassava were tested for yields at eleven different sites in Jamaica having different elevations, rainfall and soil types. From two to nine varieties were tested at each site, in a total of thirty-one plots. Planting was at the rate of 5,500 sticks per acre, about double the customary rate. Average yield with all plots weighted equally was 12.6 tons per acre, about double the national average. The most outstanding varieties were Blue Bud, a sweet variety which averaged 15 tons/acre, and Smalling, a bitter variety which averaged 13 tons/acre, other promising varieties requiring further testing are Bobby Hanson, E.P., and co-3 0. The results clearly demonstrated the significant increases in yields associated with denser planting rates. There was some indication that yields decreased above 1,900 ft. elevation. No trends with respect to soil texture or average rainfall (by sites) was identified. costs were J$2,965 with manual land preparation and J$2,490 with mechanical land preparation per acre. At 1987-88 prices, and using a conservative estimate of 10 tons/acre yields, a farm gate price of JS0.15 per pound is required to cover production costs.