Different micellar systems are characterized. Hydroformylation reactions are carried out in the most appropriate ones and are compared with hydroformylations in a non-micellar system. Reaction rates and selectivities for aldehydes are higher than the micelles. In addn. to this, olefins between C6 and C16 are successfully hydroformylated in the micellar system, whereas C8 is the highest olefin that can be hydroformylated without micelles. The behavior of the reaction in the micellar system is very sensitive to the initial compn. and reaction conditions. [on SciFinder (R)]