If you have an iPhone 4 and an Apple Developer account, then you can download the iOS 5 b1 firmware. Thanks to the iPhone Dev Team, you can also jailbreak iOS 5 b1 using RedSn0w for the Mac. Just so you know, this procedure will cause you to upgrade your baseband, which will potentially ruin your chances for an unlock. It will not hacktivate so you must have your UDID registered  with a developer and it is tethered. Supported devices: iPod touch 3G iPod touch 4G iPad 1 iPhone3GS iPhone4 (GSM) iPhone4 (CDMA) Note: RedSn0w 0.9.8b1 is purely for developers who want to develop jailbreak apps for iOS 5 and iOS 5 beta is currently available to developers only. This RedSn0w jailbreak provides tethered iOS 5 jailbreak for now. RedSn0w 0.9.8b1 will not hacktivate iPhone, iPad or iPod Touch. The iPhone Dev-Team notes that this version of RedSn0w will likely work to jailbreak future iOS 5 betas by pointing to the 5.0b1 IPSW. Download RedSn0w 0.9.8b1: Download RedSn0w 0.9.8b1 for Mac Download RedSn0w 0.9.8b1 for Windows [Coming Soon] Download iTunes 10.5 beta Download iOS 5 beta Disclaimer: This guide is for information and educational purposes only. Use it at your own risk, we cannot be held responsible if anything goes wrong. Step 1: Download the necessary files from the section above and place them in a folder on your desktop. Step 2: Connect your iPhone to the computer and launch iTunes. Select your iPhone from the devices on the left. After doing so, hold Option and click the Restore button. (Restore is preferred as it won’t create any wasted space on your iPhone.) Now navigate to the folder on your desktop and select the 5.0b1 firmware ipsw. Click the Choose button to continue. Step 3: Once iTunes has finished updating your iPhone to the desired firmware open the folder on your desktop and launch the Redsn0w application from the redsn0w folder we extracted earlier. Step 4: Once RedSn0w opens click the Browse button: Step 5: Select the 5.0b1 firmware IPSW placed in the folder on your desktop then click Open. Step 6: Once the firmware has been verified click the Next button to continue. Step 7: RedSn0w will now prepare the jailbreak data (this may take some time, just be patient) Step 8: From this window you can select the jailbreak options that you would like. Make sure Cydia is selected and click the Next button to continue: Step 9: Please plug your iPhone into the computer and make sure its OFF then click the Next button: Step 10: RedSn0w will now require you to enter DFU mode Hold down both the Home button and the Power button for 10 seconds. Release the Power button and continue holding the Home button until RedSn0w detects the device. Step 11: Your iPhone will now reboot: Step 12: RedSn0w will then begin uploading the new RAM Disk and Kernel. Step 13: Once this is complete you will be notified that RedSn0w is done. Click the Finish button. When your iPhone finishes rebooting (5 minutes or so) it will be jailbroken with Cydia on the SpringBoard. There you go! You have just finished jailbreaking iOS 5 on your iPhone 4. If you have any questions or comments, be sure to drop us the line in the section below! Share your experience with us in the comments section below. And, as usual, stay tuned for more news and info on this topic by following us on Facebook, Twitter, and/or subscribing to our RSS feed. Authors: