Understanding the performance behaviour of Java Virtual Machines is important to Java systems developers and to applications developers. We review a range of Java benchmark programs, including those collected by the Java Grande Forum as useful performance indicators for large-scale scientific applications, or “Java Grande applications”. We systematically analyse t. hese benchmarks on a collection of compute platforms including Pentium II, UltraSPARC II, Silicon Graphics, iMac and Alpha, and operating systems including Windows NT, Solaris, sand Linux, and consider differences in performance between benchmarks running on the Java Development Kit (JDK) versions 1.1. 6 and 1.2. We also analyse some benchmark programs we have developed to augment existing collections. We observe some general trends in the performance of Java on various platforms and also conduct some comparisons between benchmarks written in Java and in traditional languages such as C and Fortran. We discuss performance variations across syst. ems and t. he implications of Java systems performance for those developing scientific applications.