'Ecological imperialism: The biological expansion of Europe, 900-1900', by A. W. Crosby, is a cogently argued and well written book. The main thesis of the book is that the expansion by Europeans to the Americas, Australia, New Zealand, and a few other enclaves (what Crosby calls the Neo-Europes) wouldn't have succeded if the biota the Europeans brought with them had not suceeded. This biota included not only humans, of course, but pathogens, weeds and grasses, and horses, cattle, goats, and pigs, among the most important. Crosby addresses the reasons why this biota was so succesful in the new territories, and concludes that, in general, the climatic regimes there were sufficiently similar to those of its European origins and the indigenous biota was so 'naive' that 'victory' was almost assured to the invaders. To be sure, this is not an original conclusion, but the wealth of data Crosby uses, along with his synthetic power and sense of humor, makes of this book an enjoyable and thought-provoking read. People interested in searching for the biological causes of the successes (and failures!) of Europeans in the world should read this engaging book.