Three isogenic progenies of Red Bourbon coffee (Coffea arabica L.var. bourbon (B. Rodr.) Choussy) were investigated in relation to several characteristics in a balanced lattice experiment with 16 entries, five replications, each plot with four individual plants. Two of these isogenic progenies were obtained by artificial self-pollination of two plants which were derived from haploid sporophytes after their chromosomes were duplicated (357-21 and RP 13). The third isogenic progeny is the F1 of the hybrid between those duplicated plants (H 1934). Among the remaining 13 entries of this trial more attention was given to the following progenies of Red Bourbon coffee: 959, S0 from open pollinated seeds taken in a private farm; 43-18-11, selfed S3 from a selected plant; 43-7-7-15 and 43-7-19-13, selfed S4 progenies of similar pedigrees. Plant height was measured for all entries five years after transplantation to the field. It was observed that the F1 did not show heterosis for this characteristic, its average height being intermediate between those of the two isogenic progenies. The within plot variance presented by the F1 is equal to that of one of the pure lines and close to that of the other. The average height presented by the S3 and the S4 progenies originally derived from plant C 43 suggests that successive selfing does not reduce plant height (Table 3). Total yields in kilograms of riped fruits of individual plants were recorded for the first three years of crops. The mean yield of the F1 is higher than those of the two isogenic lines, although this difference is not significant. The within plot variance of yields is smaller for the F1 than for the two pure lines, but again the differences are not significant. When separate analyses were made for the annual crops of the three isogenic progenies, it was seen that the smallest within plot variance was presented by the F1 in two of the three years. The within plot variances for the total yields of the S3 and S4 progenies were higher than those presented by the isogenic progenies, showing a tendency to become larger with successive selfings (Tables 4 and 5). Observations were also made on the percentages of three different seed types produced by coffee plants, namely, the flat, normal seeds, "moca" (peaberry) and "concha" seeds. "Moca" seeds result from the development of a single ovule after a precocious abortion of the second ovule in the ovary. "Concha" seeds are those born from independent ovules which may eventually occur in the same fruit lo-cule. Abnormal frequencies of these abnormal seed types are clearly under genetic control and apparently the percentage of "moca" beans is more subjected to environmental influences. Lower percentages of "moca" seeds were found for the F1 hybrid than for the two pure lines. The value of the F1 variance for percentage of "moca" is intermediate between those of the pure lines and closer to the highest vafcie. Higher variances in the percentage of this seed type were found for the other progenies, showing also a tendency to increase with more generations of selfing. The percentages of "concha" seeds were not different among the three isogenic lines, the F1 variance for this seed type being intermediate. Higher variances for the percentage of "concha" seeds were found for the other progenies, together with an indication that successive selfings may reduce the incidence of this seed types (Tables 6 and 7). Seed size was graded for all plants during the three years of crop in a series of sieves differing by 1/64 of an inch. No differences were noticed between isogenic progenies, although the F1 variance for seed size was lower (Table 8). It is concluded that a definite trend can not be observed for the variability within isogenic progenies of the arabian coffee plant, which is a predominantly autogamous species. Depending on the characteristic under observation, the variances of the F1 hybrid may be lower, equal to or higher than the variances presented by the isogenic progenies of the homozygous plants that entered the cross. (Table 9). Although these data refer only to the first three years of crop, it may be pointed out that no instance was found where the Fx presented higher variances than those of the two isogenic progenies.