This seems wield to me. I hope to find somebody has the same experience could help me. I am using FedExAPI.JAR in one of my class Shipping.java. I call a constructor FedExAPI() in Shipping.java. The classpath environment was set correctly because the Shipping.java could be compiled without complain. However the FedExAPI() constructor could not be found at runtime giving me an exception like this 001.10.15 12:08:39: Multiserver,ERROR: Unable to change application to running state: com/fedex/api/FedExAPI 2001.10.15 12:08:39: Multiserver,ERROR+ java.lang.NoClassDefFoundError: com/fedex/api/FedExAPI 2001.10.15 12:08:39: Multiserver,ERROR+ at dCommerce.business.Shipping.(Shipping.java:15) What is wrong here? Shipping.class runs well on a test server with same environment of Linux6.2, jdk1.2.2 and pentium iii. Any hint will be appreciated Zhenhai