One of the most intriguing and crucial problems of the prebiotic evolution and the origin of life is the explanation of the origin of biohomochirality. A scheme of conversions originated by formaldehyde (FA) as hypothetical primer of biohomochirality is proposed. The merit of FA as executor of this function is based ‐inter alia ‐ on the distinguished role of FA as one of the earliest and simplest molecules in both warm, terrestrial and cold, extraterrestrial scenarios of the origin of life. The confirmation of the role of FA as primer of biohomochirality would support the option of an RNA world as an alternative to the protein world. The suggested hypothesis puts forward for the first time a concrete sequence of chemical reactions which can lead to biohomochirality. The spontaneous breaking of the mirror symmetry is secured by the application of the well‐known Frank scheme (combination of autocatalysis and ‘‘annihilation’’ of L and D enantiomers) to the series of interactions of FA ‘‘trimers’’ (i.e. C3H6O3compounds) of (aaa), (apa) and (app) types, where the monomeric groups (a) means ‘‘achirons’’ (a=CHn, n≥2 and C=M, M=C,O) and (p) mean ‘‘prochirons’’ (p=HC*OM, M=H,C). ©1996 American Institute of Physics.