Although several methods have been developed for producing haploid plants, the in vitro techniques are much more efficient than inter-specific hybridization or treatment with plant-growth regulators, temperature or irradiation. Androgenesis is the most universal of these techniques but ovule culture and the bulbosum method could complement or replace anther culture in those species or genotypes with less responsive male gametes. Genotype, environment, physiological status of the donor plant, and culture conditions and components all need to be taken into account when developing procedures for producing haploid and dihaploid plants. Suitable methods are already well established for a number of important crops. However, many problems, related to regeneration frequency, gametoclonal variation and albinism, are still unsolved. It is now clear that haploids and dihaploids form the ideal system for genetic manipulation in plants. Their key role in producing new theoretical and applied knowledge in plant science is an important aspect of our review.