Using the currency demand and DYMIMIC approaches estimates are presented about the size of the shadow economy in 22 Transition and 21 OECD countries. Over 2001/2002 in 21 OECD countries is the average size of the shadow economy (in percent of official GDP) 16.7% of “official” GDP and of 22 Transition countries 38.0%. The average size of the shadow economy labor force (in percent of the population of working age) of the year 1998/99 in 7 OECD-countries is 15.3% and in 22 Transition countries is 30.2%. An increasing burden of taxation and social security contributions combined with rising state regulatory activities are the driving forces for the growth and size of the shadow economy (labor force).