Four generations of half-sib family selection for yield of digestible organic matter have been completed, from an initial population which included marrow-stem kales, thousand-head kales, curled kales, Brussels sprouts and cabbages. Relative to the mean yields of two control cultivars the population means were: 106% (gen0), 122% (gen1), 128% (gen2), 111% (gen3) and 103% (gen4). These initially encouraging and then disappointing results are discussed along with suggestions for improvements in the population improvement scheme, particularly with respect to the assessment of genotype-environment interactions.