I tried following all the directions. Installed the SDK, eclipse v3.7.1 and when I tried to install the ADT inside Eclipse I get this message:
"Missing requirement: Android Development Tools 15.0.1.v201111031820-219398 (com.android.ide.eclipse.adt.feature.group 15.0.1.v201111031820-219398) requires 'org.eclipse.wst.sse.core 0.0.0' but it could not be found"
Not sure if I have the wrong version of Eclipse or what? Any help would be appreciated.

I have the same problem! I am trying to install the ADT on a new machine.

Me, too! Fresh install, just downloaded SDK, Eclipse, JDK, et al this morning. No problem until I reached this step:

Downloading the ADT Plugin
6. In the next window, you'll see a list of the tools to be downloaded. Click Next.

Can't click Next unless I uncheck Android Development Tools:

Details
Cannot complete the install because one or more required items could not be found.
Software being installed: Android Development Tools 15.0.1.v201111031820-219398 (com.android.ide.eclipse.adt.feature.group 15.0.1.v201111031820-219398)

What Eclipse package did you (both) download and install to install the plug-in into?

I think I figured it out. You have to start Android SDK manager and Eclipse "Run As Administrator" ie right click on the exe file and select "Run As Administrator". Hope that helps others.
Nitro

I followed same steps reported by nitro - worked like a champ. Start SDK Manager, run Eclipse as admin. Thanks everyone.

I have exactly the same error when trying to install the ADT plugin in Eclipse on Ubuntu 11.10. I installed Eclipse 3.7.0 from the Ubuntu repository. I have sun-java6-jdk installed. Any suggestions will be much appreciated.

For some reason, I couldn't install ADT to 64-bit version of Eclipse but with 32-bit version, it worked without a hitch!

clanlaw wrote:I have exactly the same error when trying to install the ADT plugin in Eclipse on Ubuntu 11.10. I installed Eclipse 3.7.0 from the Ubuntu repository. I have sun-java6-jdk installed. Any suggestions will be much appreciated.

OK, sorted it, via Help > Install New Software, clicked Available Software Sites and added http://download.eclipse.org/releases/indigo and then tried again and all was well.

Nice work Nitro. Run as admin fixed my install also.

clanlaw wrote:

clanlaw wrote:I have exactly the same error when trying to install the ADT plugin in Eclipse on Ubuntu 11.10. I installed Eclipse 3.7.0 from the Ubuntu repository. I have sun-java6-jdk installed. Any suggestions will be much appreciated.

OK, sorted it, via Help > Install New Software, clicked Available Software Sites and added http://download.eclipse.org/releases/indigo and then tried again and all was well.

Thank you sir.

I don't know how you figured this out, but I'm glad you did. God bless Google.

cranknode wrote:I followed same steps reported by nitro - worked like a champ. Start SDK Manager, run Eclipse as admin. Thanks everyone.

I followed the same steps, but still error. I am running on Win7 64bit.

Had the same problem, followed nitro's steps but on my Ubuntu 11.10 right clicking the exe just starts Eclipse without "Run As Administrator" option. Sooo... opened up a terminal window, navigated to /usr/lib/eclipse and entered "sudo eclipse". BINGO!! Thx nitro

I am having problems/trouble downloading the ADT...
I downloaded and installed:
jdk-7u2-windows-i586
installer_r16-windows
eclipse 3.7

I have tried running eclipse as admin and without...
Will not download from http://dl-ssl.google.com/android/eclipse or https://dl-ssl.google.com/android/eclipse

I have even downloaded:
ADT-16.0.1
And followed Alt. install instructions

BUT I still get:
Cannot complete the install because one or more required items could not be found.
Software being installed: Android Development Tools 16.0.1.v201112150204-238534 (com.android.ide.eclipse.adt.feature.group 16.0.1.v201112150204-238534)
Missing requirement: Android Development Tools 16.0.1.v201112150204-238534 (com.android.ide.eclipse.adt.feature.group 16.0.1.v201112150204-238534) requires 'org.eclipse.wst.sse.core 0.0.0' but it could not be found

Thk U but I got it.....fluke.

I opened Andriod SDK Manager and ran Eclipse as Admin
Then Help -> Install New Software...
In the "Work with:" address bar use "-- All Available Sites --"
make sure you have added "http://dl-ssl.google.com/android/eclipse" to the list of "Available Software Sites"