New cyclic photoionization mechanisms of acridine and its derivatives and xanthone were investigated by nanosecond laser flash photolysis with optical detection. Photoionizations of the investigated substances as electron donors proceed either via cyclic mechanisms in aqueous SDS micellar solutions or via linear mechanisms in alcohol-water mixtures. This provides a strong evidence that SDS can act as reducing component in the cyclic photoionization. Furthermore, the photoionization quantum yields in SDS are greater than those in alcohol-water mixtures. Photoionizations of acridone and N-methylacridone in aqueous SDS solution proceed via a cyclic mechanism involving their singlet state, whereas cyclic photoionization of xanthone occurs via its excited triplet state. The solutions of differential equations for the kinetic models corresponding to these mechanisms give closed form expressions that could be fitted well to the experimental data. Cyclic photoionizations of acridine and proflavine proceed via both singlet and triplet state. The solution of the rate equations corresponding to this mechanism was carried out numerically. The photoionization of an electron acceptor (e.g., xanthone) in the presence of an electron donor (e.g., triethylamine, or 1,4-Diazabicyclo[2.2.2]octane) at high laser intensity occurs via a cyclic mechanism. At low to moderate quencher concentration, a combined linear and cyclic photoionization of xanthone/amine system in methanol-water mixtures can occur. In two-pulse two-colour experiments (308/532 nm), a linear two-photon ionization of the radical anion of xanthone was found at 532 nm. Only at high laser intensity, it is possible to differentiate between a linear and cyclic photoionization process.