The behaviour of alkaline salts of some aroyl-hydrazine-carbodithioic acids [comp. Ia,b,c,] and derivatives of 1,3,4-oxadiazole [comp. IIa,b,c, e IIIa,b,c] , has been studied, on the capability of lymphoblasts in vitro, in consequence of stimulation by some mitogen agents (PHA, PWM). It has been pointed out that the considered compounds inhibit the cellular mitosis in variable percentage in relation to their structure and to the used mitogen agent, frequently causing some mitogen-like morphological modification, also revealable under a optical microscope. The higher inhibition has been obtained by the Ic, IIc, and IIIc compounds, in which Ar is the 3,4-dihydroxymethylenephenyl radical, proving selective, in some cases, for the T lymphocytes.