Data collection is a necessary step in data mining process. Due to privacy reasons, collecting data from different parties becomes difficult. Privacy concerns may prevent the parties from directly sharing the data and some types of information about the data. How multiple parties collaboratively conduct data mining without breaching data privacy presents a challenge. The objective of this paper is to provide solutions for privacy-preserving collaborative data mining problems. In particular, we illustrate how to conduct privacy-preserving naive Bayesian classification which is one of the data mining tasks. To measure the privacy level for privacy- preserving schemes, we propose a definition of privacy and show that our solutions preserve data privacy.