The morphological and cytogenetic features of the natural and artificial hybrids between tetraploid H. jubatum (2n=28) and hexaploid H. parodii (2n=42) have been studied. The hybrids, which were pentaploid, approached in quantitative morphological traits the parental species which contributed a higher number of genomes (H. parodii). The meiosis was highly irregular and variable. The average cell had about half of its chromosomes as univalents, slightly less than half were forming bivalents and the few remaining, multivalent associations (III, IV, very occasionally V). Electrophoresis of seed proteins revealed that homology of fractions in both parental species is not high (coefficient of similarity=47.82%). Chromosome pairing probably results from both allo- and autosyndesis. In contrast to the not too close phylogenetic relation of both species as revealed by morphology, chromosome behaviour in the hybrid and protein homology, the crossability of both species is rather high.