The effect of seven planting densities on yield and witches' broom disease incidence in hybrid cacao (Theobroma cacao) trees in the Brazilian Amazon was investigated. Data collected over a three-year period showed that it was possible to optimize regional cacao yield by high planting densities (2500 and 1666 trees ha−1) and that there was no density × year interaction. However, high planting density also favoured witches' broom incidence. A growing regional interest in planting cacao clones at high planting density should be pursued with caution, since high planting densities of clones in environments under strong pressure of selection for the witches' broom pathogen, such as in the Amazon region, are still a risky strategy. Alternatives to the high planting density system are presented and discussed.