Torilis arvensis (Huds.) Link has been collected in the northeast of Buenos Aires province, Argentina, in urban areas, confirming its existence in the country as was predicted by Pedersen's contribution to the Flora Ilustrada de Entre Rios. This is a rare species in the United Kingdom, but classified as harmful plant in Spain and as a weed in several states of the United States of America. In our country, is regarded as an introduced naturalized plant, which may behave like invasive (plant strategist R) because, among other features, it is a therophyte producing abundant viable seeds. The present paper describes and illustrates this species, including the pollen grains which were studied using optical and scanning electron microscopy. [ABSTRACT FROM AUTHOR]