The Japanese system of lean production is the most efficient way for manufacturing cars argue Womack et al. in their MIT study The Machine that Changed the World (1990). They strongly recom- mend Western companies to learn and adapt to it, if they want to survive in the 1990s. This paper shows that lean production per se is not sufficient to explain the Japanese superiority unless favourable macroeconomic and microeconomic conditions prevail (precisely as for mass production). It also points to some methodological and analytical deficits in the MIT study.