It's not up to me to allow or not allow. It's not my home. But, for security reasons, when I enter a home with buyers, I always lock the door behind me, and keep the key with me. If we're upsatairs looking at bedrooms, and the door bell rings, they just have to wait. I don't even want to have conversation with other agent. And even if agent and buyers are waiting on porch, I lock house and put key back in lock box, then that agent has to remove the key so the agents info gets recorded for the listing agent.

Tony - I am sorry, but I would not allow other agents and their clients to show the home if I am there with my clients. Too many things could go wrong, one of them being what Vera Gonzalez experienced. I do the same thing as Jeff Pearl said, and put the key back in the lockbox so the other agent has to record when they take the key back out.

It is not only a respect thing (potential buyers should be able to look at a home on their own), but a safety thing.

If I am on the waiting end, I will wait my turn. If it screws up my schedule the rest of the day, then I just have to deal with that.

I am sure this can be a problem.

I ask them to wait. When I am done I invite them in. My clients do not need to feel like they are being watched or rushed.

I dont and I will tell you why I dont. My clients know we never take longer than 15 minutes. If they have questions we an address them outside.  About 3 years ago in the dead of winter an agent asked if their client could come inside as well  because it was cold. my buyer felt bad and said sure.  Her buyer started in on my client with the do not bother writing this I have cash The agent also started in. It was ridiculous. Safety wise I would not either, How do I know they didn't meet them for the first time at the house?

Sometimes double booking happens.  I haven't a problem with another group looking upstairs whilst I'm down. Or, inside whilst outside.  Stuff happens so we deal with it.

If it is my own listing, the door gets locked.

Generally not a problem here.

We are seeing many overlapping showings, and if we did not let everyone in, there could be a very long line outside a listing.   When no one else is waiting, I do lock the door behind me and have the key in my hand.

I don't have a problem with it, as long as the other agent starts their clients in a separate area of the house 

I would ask them to respect our time in the home; however I doubt I would throw a punch if they insisted.

No.  And I don't let them in without the agent putting their code into the lockbox.

Usually for safety sake once we are inside the home I lock the front door.  Not because I don't want other agents in but because of safety.  I usually have the key in my pocket as we walk through. In our market it is customary for the second agent to wait until the one inside comes out.

Did I arrive on time?
YES - I advise the waiting agent the process takes 20 minutes (minus time already spent"
NO - The conflict was created by an agent not managing their business. I can be a dolt and blame someone else or concede to the problem I created and allow the 2nd agent to log in via the ebox.

Did the other agent arrive early? - Somewhat irrelevant if Central showing was used. But if they are early, I suggest they need to wait until my show time has expired.

It is 'MY' listing? That changes everything and different rules and outcomes are expected.

I'm admittedly a huge hypocrite on this subject. 

I'll try to negotiate my way in to a house if I arrive and another agent is already in there showing; to stay on schedule.

But, when I arrive to a home, I keep the front door locked and ignore the doorbell, because I want my clients to have privacy whenever possible.

I know, I know, but that's the truth of it.

Depends  I ask other agents if the do not mind

Open home? or one with a lock box and you ended up there at the same time?