In the following two cases, if Customer is disposable (implementing IDisposable), I believe it will not be disposed by ASP.NET, potentially being the cause of a memory leak: [WebMethod] public Customer FetchCustomer(int id) { return new Customer(id); } [WebMethod] public void SaveCustomer(Customer value) { // save it } This flaw applies to any IDisposable object. So returning a DataSet from a ASP.NET web service, for example, will also result in a memory leak - the DataSet will not be disposed. In my case, Customer opened a database connection which was cleaned up in Dispose - except Dispose was never called resulting in loads of unclosed database connections. I realise there a whole bunch of bad practices being followed here (its only an example anyway), but the point is that ASP.NET - the (de)serializer - is responsible for disposing these objects, so why doesn't it? This is an issue I was aware of for a while, but never got to the bottom of. I'm hoping somebody can confirm what I have found, and perhaps explain if there is a way of dealing with it.