[en] Complex formation equilibria of beryllium(II) with five aliphatic α-hydroxycarboxylic acids, viz. glycolic (HL), lactic (HL), 2-hydroxyisobutyric (HL), L(+)-tartaric (H₂L) and citric (H₃L) acids, were studied by means of potentiometric (glass electrode) titrations at 25 deg. C in an ionic medium of 0.5 M NaClO₄. The titrations were performed in a pH range in which precipitation did not occur. Glycolic and 2-hydroxyisobutyric acid complexation with beryllium(II) are described by the formation of three rather weak complexes, namely BeL⁺, BeL₂ and Be₃(OH)₃L²⁺. Lactic acid was not found to form BeL₂ species. The equilibrium model for tartaric acid constitutes of the three complexes mentioned above together with two deprotonated complexes Be(H_-1L)₂^4- and Be₃(OH)₃(H_-1L). Citric acid was found to form also protonated and binuclear species prior to the formation of hydrolyzed complexes. The p,q,r analysis gave the following set of complexes: BeL^-, BeL₂^4-, Be₂L₂'²'2-, Be₂H_-2L₂^4- and Be₂H_-3L₂⁵ stability constants for these complexes with their standard deviations are reported. (au) 23 refs