1. Unlike chloroplasts, submitochondrial particles are not uncoupled by nigericin + KC1 or NH,CI. Also the uncoupling effect of lipophilic anions is largely independent of the addition of weak bases.2. Low concentrations of permeant anions cause a shift of the steady-state energy level rather than a cycle of energy utilization. The degree of inhibition of ATP synthesis by tetraphenylboron is larger than required for the uptake of the anion.3. Lipophilic anions such as bromthymolblue, bromcresolpurple, and 8-anilino-I-napthalene sulphonate cause a pH-independent, 50 uncoupling in submitochondrial particles at concentrations of 3, 30 and 30 pM, respectively. The passive interaction of bromthymolblue and bromcresolpurple appears as a pH-dependent distribution between two phases. ATP causes a pH-independent slight shift in the anion distribution, with negligible anion accumulation.4. Addition of amines to energized submitochondrial particles results in two types of effects : uptake of amines and uncoupling. While in chloroplasts amine uptake and uncoupling are closely associated, this is not the case in submitochondrial particles. The uncoupling effect is observed only with lipophilic and not with hydrophilic amines, and the degree of uncoupling increases with the lipophilicity of the amines. The amine uptake, on the other hand, is accompanied by negligible uncoupling.5. While the uptake of amines is dependent on the presence of non-permeant anions, such as C1-, the uncoupling effect is independent of C1-. Furthermore the amine uncoupling is markedly enhanced by lipophlic anions.6. The view is discussed that the uncoupling effect of lipophilic anions and lipophilic amines in submitochondrial particles is due to a catalytic energy dissipation rather than to a stoichiometry energy utilization. The molecular mechanism of uncoupling presumably involves a cycling of charges after a perturbation of the membrane structure.When active transport takes place other energylinked reactions are inhibited [l]. Although the inhibition is loosely indicated as "uncoupling" it has been realized that the uncoupling due to active transport is different in nature from the classical uncoupling. In fact the former is due to stoichiometric energy utilization for ion transport while the latter is due to catalytic energy dissipation. The former is accompanied by a stoichiometric cycle of energy utilization, denoted as state 4-state 3 -state 4 transition, while the latter is accompanied by a shift of the steady-state energy level. While the distinction between stoichiometric energy utilization, linked to ion uptake, and catalytic energy dissipation, due to damage or uncoupler cycling, is clearly established in intact mitochondria, this is not the case in submitochondrial particles.Skulachev el al.[2] reported an uncoupling effect of lipophilic anions in submitochondrial particles and suggested it be equivalent to the energy utilization accompanying cation uptake in mitochondria. Christiansen et al.