Thank you one and all - about a dozen responses via TWL or e-mail - for exactly the info I needed, without which I might never have found my way. You will infer from the slight but important change of subject line that there's more to this than wiring. The utility of the "instruction" manuals is about zero! I have two more questions below, but for others who might wish to have a summary, the recap of what you collectively advised is: 1) the serial port is male and the plug is female. Looking at the plug from the back where the pins protrude for soldering, the number 1 pin is at the upper left and the numbering runs from left to right across the top and then from left to right across the bottom; 2) the Garmin wiring is: blue (data out) goes to pin 2, brown (data in) goes to pin 3, and black (ground) goes to pin 5. (Note that the same black wire is also used for the connection to 12 v neutral.) 3) In Navtrek, go to Tools > Options and ensure that under tab "Ports Configure" the box beside Com1 is checked, then click on the "Ports Prioritize" tab, click on the "Add" down arrow, and add "GP-GPS". Click on "Apply", and close the Options box. 4) The GPS 128 itself has to be configured by going to its "Main Menu Page" then to "Interface" and then entering 1) none/nmea; and 2) 4800 baud. 5) Finally, if the laptop is an IBM Thinkpad - mine is - ensure the Infrared port is disabled in order to be able to use the com port at the rear of the computer. Easy when you know all the steps. Thanks again. Next Problem: When trying to upload/download waypoints from within Navtrek, a dialog box comes up that says it can't do so "while sending or receiving NMEA data through the serial ports. Please disable the serial port via Tools>Options>ports I/O before uploading/downloading". (That message appears even when the GPS is physically disconnected.) Moreover, while the Ports I/O function must be in there somewhere, I have yet to find it. If I simply uncheck the Com1 box, the program warns me that it cannot find Com2, so clearly a port has to be enabled. Is it asking me to delete the GPS? Either way, the instruction makes no sense. If I disable either the port or the GPS, how do I transfer data? The other question is: can routes and waypoints be entered into the Garmin directly - which would be tedious in the extreme - or directly from a computer without going through Navtrek? Cheers, Garrett