An extensive project concerned with coffee breeding was organised, in 1933, in the Genetics Division of the Instituto Agronômico. Among various lines, it was decided to make a comparative study between progenies, obtained through artificial selfings, and hybrids derived from crossings of the same mother plants which furnished the progenies, all belonging to Coffea arabica L. var. bourbon (B. Rodr.) Choussy. The productivity and the height of the plants were compared, in order to find out, whether these characters display any heterosis effect in the hybrids, and also whether the first artificial selfing has any detrimental influence. The mother plants utilised in these studies are derived from a common origin, the seeds from which they developed having been harvested from a small coffee plantation near Campinas. Both progenies and hybrids, were planted in 1938, without replications, in rows of 20 plants, in one of the coffee breeding plots of the Central Experiment Station, at Campinas. Four progenies and eleven hybrids were used in this investigation, the hybrids being formed of five groups of reciprocal crosses and a single hybrid, as not enough seed of its reciprocal was available for planting. The analysis of the yield data was carried out in two parts : the first one comprised the first six years of consecutive yields (1939-1944) collected from the 20 plants of cach group (with the exception of one of the hybrids of which only 18 plants were available) ; the second, covering a total period of 12 years (1939-1950), only concerned the yield of two groups of plants, selected in the year 1944, based on their high mean annual yields, fifteen belonging to the progenies and twenty three to the hybrids. The statistic analysis of their yield and of their variability revealed, in the first case, that no differences exist between progenies and hybrids, not only when the two groups are compared, but also when, each time, two progenies are compared with their reciprocal hybrids. Even after twelve years of production, no differences were found in respect to yield. The height of the plants was measured in 1950. The analysis of the data showed that no statistical difference exists between the mean height of progenies and hybrids ; however the hybrids revealed a higher variability of this character. The difference in variability was particularly manifested in two instances, where two progenies were compared with their reciprocal hybrids. It is therefore concluded that in the material investigated no heterosis ocurred in relation to yielding capacity and plant height and that selfing has no detrimental effect on these characters. This might be explained considering that C. arabica is predominantly autogamous and that the four individuals, whose progenies and hybrids were used in this study, have a common origin and most probably are of very similar genetic constitution.