ECONOPHYSICS is the application of physics techniques to economics problems. Like a collection of electrons or a group of water molecules, the world economy is a complex system of individual members (in this case, countries) that interact with each other. In a situation that many experimental physicists would surely envy, the world economy produces an incredible amount of data--one year of US stock-exchange transactions results in 24 CD-ROMs of data. These data provide the opportunity for extensive statistical analyses which can lead to a better understanding of the behavior of these complex systems. In an earlier study of business firms (Stanley et al, Nature, 29 Feb. 1996), physicists and economists found that the probabilities associated with observing a given growth rate for a firm could be described with a single mathematical function for firms of all types and sizes (from sales of $100,000 to $1 trillion). Furthermore, they found that the width of the curve showing the probability distribution follows a "power law,"in which the width is proportional to the firm size raised to a power of approximately 1/6. Now, a Boston University-MIT physics team (Youngki Lee, Boston University, 617-353-8051) collaborating with a Harvard economist (David Canning, 617-495-8401) has found the same universal patterns and power law for the fluctuations in the growth rates of the gross domestic products (GDP) of 152 countries from 1950-1992. (Lee et al., Physical Review Letters, 12 October 1998.) These models raise the exciting possibility that complex human organizations can be studied with methods and concepts developed in statistical physics. (Amaral et al., Phys. Rev. Lett.,16 Feb. 1998.)