When I use boost::serialization on MS VS 2005 I have some warnings even on level 3. The warnings are: 1) warning C4267: 'argument' : conversion from 'size_t' to 'std::streamsize', possible loss of data j:\thirdparty\boost_1_34_1\boost\archive\basic_binary_oprimitive.hpp 136 2) warning C4267: 'initializing' : conversion from 'size_t' to 'std::streamsize', possible loss of data j:\thirdparty\boost_1_34_1\boost\archive\basic_binary_iprimitive.hpp 144 3) warning C4267: '=' : conversion from 'size_t' to 'std::streamsize', possible loss of data j:\thirdparty\boost_1_34_1\boost\archive\basic_binary_iprimitive.hpp 154 4) warning C4267: 'initializing' : conversion from 'size_t' to 'unsigned int', possible loss of data j:\thirdparty\boost_1_34_1\boost\serialization\collections_save_imp.hpp 38 [And this seems to me an obvious error, the variable "count" should be declared as "Container::size_type".] 5) warning C4996: 'std::basic_streambuf<_Elem,_Traits>::sgetn': Function call with parameters that may be unsafe - this call relies on the caller to check that the passed values are correct. To disable this warning, use -D_SCL_SECURE_NO_WARNINGS. See documentation on how to use Visual C++ 'Checked Iterators' j:\thirdparty\boost_1_34_1\boost\archive\basic_binary_iprimitive.hpp 148 [This seems to be MS specific problem which should be solved on project level.] 6 ) warning C4996: 'std::basic_streambuf<_Elem,_Traits>::sgetn': Function call with parameters that may be unsafe - this call relies on the caller to check that the passed values are correct. To disable this warning, use -D_SCL_SECURE_NO_WARNINGS. See documentation on how to use Visual C++ 'Checked Iterators' j:\thirdparty\boost_1_34_1\boost\archive\basic_binary_iprimitive.hpp 159 [This seems to be MS specific problem which should be solved on project level.] Can anything be done (especially in case of warning 1-4)? Adam Badura