I got the answer to my own question: ex.ToString where ex is the exception object.
Public Class Form1
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Try
Dim x As Integer = 5
Dim y As Integer = 0
Dim result As Integer
result = x / y
Catch ex As Exception
MessageBox.Show("ex.ToString: " & ex.ToString)
End Try
End Sub
End Class
I hope this helps others.