Composition of nutrient media, flower bud size, cold pretreatment, heat shock stress, and ethylene inhibitor could have marked effects on microspore embryogenesis. No microspore-derived embryos (MDE) were formed when microspores were isolated from radish (Raphanus sativus L.) flower buds of 1.0-2.5 mm in size, whereas MDE were formed with microspores isolated from 2.5-4.5 and 4.5-6.5 mm flower buds. The microspores isolated from 2.5-4.5 mm flower buds showed high embryo yields. When the isolated microspores were washed with Nitsch & Nitsch (NLN) liquid medium containing 130 g‧L-1 sucrose (NLN-13), the yield of MDE increased significantly when comparing with washing using B-5 liquid medium containing 130 g‧L-1 sucrose.Microspores cultured on half strength NLN liquid medium containing 0.05 mgL-1 silver nitrate (AgNO3) produced the most MDE, showing a more than two-fold increase in yield compared to those cultured on medium without AgNO3. A heat shock pretreatment of microspores at 32°C for 24 h gave high-frequency production of MDE when compare to higher or lower temperatures; no MDE were formed at 42.5°C. Microspore viability is known to decrease rapidly with storage; however, in this experiment, microspore viability was maintained for 24 h at 4°C without media. A polyploidy test indicated that 19.7% of the microspore-derived plants were double haploid, other plants were haploid, and chimeras were haploid and diploid. This protocol is thought to be very useful for efficient production of homozygous lines that is critical for the production of radish F1 hybrids