Hi Sviatlana,

DefaultMembershipProvider doesn't have deleted user event, but you can create your own membership provider.
I'll use AlloyTech as a sample project, and extend SqlServerMembershipProvider:

1. Inside Business folder, create CustomMembershipProvider:

using System.Web.Providers;

namespace AlloyTech.Business
{
    public class CustomMembershipProvider : DefaultMembershipProvider
    {
        public override bool DeleteUser(string username, bool deleteAllRelatedData)
        {
            // TODO: cleanup code
            return base.DeleteUser(username, deleteAllRelatedData);
        }
    }
}

2. In web.config, register a new membership provider and set it as default one:

<membership defaultProvider="CustomMembershipProvider" userIsOnlineTimeWindow="10" hashAlgorithmType="HMACSHA512">
  <providers>
    <clear />
    <add name="CustomMembershipProvider" type="AlloyTech.Business.CustomMembershipProvider, AlloyTech"
          connectionStringName="EPiServerDB" enablePasswordRetrieval="false" enablePasswordReset="true"
          requiresQuestionAndAnswer="false" requiresUniqueEmail="false"
          maxInvalidPasswordAttempts="5" minRequiredPasswordLength="6" minRequiredNonalphanumericCharacters="0"
          passwordAttemptWindow="10" applicationName="/"/>
		  
    ...
  </providers>
</membership>

3. In admin mode, if you get an exception when you try to create / delete user, just restart the IIS (or kill IIS Express Worker process from task manager)

That's it. Hope it helps :)

Thank you very much!