A series of new pyrrolidinium salts (PYE-n) was synthesized for potential application in agrochemistry. They differed in the number of carbon atoms in the alkyl chain (n = 7, 9, 11, 13 and 15). These salts may also be used as effective antioxidants since they include a substituted free radical scavenging group. The aim of these studies was to determine the concentration level at which PYE-n can be possibly used as biocides and to examine their antioxidative capacities. Biocidal activity was determined by measuring PYE abilities to hemolyze pig erythrocytes, to influence cucumber (Cucumis sativus) growth and its membrane properties, and to influence the main transition temperature of DPPC liposomes. Measurements of fluidity changes in the ghost erythrocyte membrane induced by PYE compounds were also done. Three probes: DPH, TMA-DPH and laurdan were used in the measurements. The results of those experiments showed that the pyrrolidinium salts studied exhibit fairly good membrane activity, which makes them potentially useful agrochemical agents. Antioxidative capacity of PYE-n was determined by measuring the inhibition of the autooxidation of linoleic acid, tested in radical chromogen ABTS^•+ cation decolorization assay, and by measuring the protection of erythrocyte membrane lipids against UV irradiation. All the methods used to check the potential antioxidative properties of PYEs showed that they can be used as very good free radical scavengers.