Hi, Steve. Give this a try.

using System;

namespace ConsoleApplication1
{
  class Test
  {
    [STAThread]
    static void Main(string[] args)
    {
      DerivedClass test1 = new DerivedClass();
      DerivedClass test2 = new DerivedClass("test2");
    }
  }

  public class BaseClass
  {
    public BaseClass(string Argument)
    {
      Console.WriteLine("BaseClass Constructor with argument - " + Argument);
  }

  public BaseClass()
  {
      Console.WriteLine("BaseClass Constructor (no arguments)");
    }
  }

  public class DerivedClass : BaseClass
  {
    public DerivedClass(string myParm) : base(myParm)
    {
      Console.WriteLine("DerivedClass Constructor - " + myParm);
    }

    public DerivedClass() : base()
    {
      Console.WriteLine("DerivedClass Constructor (no arguments)");
    }
  }
}

Kelly

>When I instantiate the derived class, I want to invoke the base class's constructor, passing the optional argument but can't seem to figger out how this is done.