Nearly 40 years have passed since the publication of Rubin's renowned study on Paraguayan bilingualism. The present study compares the results of surveys conducted in the years 2000-2001 with data from Rubin's 1960-1961 investigation. The main objective of this study is to examine the linguistic changes that have occurred in four decades and the causal factors of these changes. Lastly, the directionality of bilingualism in Paraguay will be discussed (bilingualism, language shift, language maintenance, linguistic domains, Spanish, Guarani). (Contains 4 tables and 4 notes.)