I am working on writing a fairly simple package that defines several classes. However, there are several other packages that deal with the same types of data, so I would like to methods for coercing my classes to those of the other packages. Easy enough. However, I would really like to just "suggest" those other packages, as my own doesn't rely on them at all. If I do so and the other packages are not available and loaded, I get warnings on loading my own package that the classes from the foreign packages are not available. I understand that these messages are not significant, but is there a way to suppress them on loading. As far as I can tell, this is specific to S4 coercion methods where the classes to coerce to or from may not be loaded or defined at the time of loading a package. Any hints? (In other words, what did I miss in the documentation....) Thanks, Sean