Because the year-old Circumvesuviana topic is closed, I'll start another one to provide an update on finding a schedule for that elusive train system (old links pointed to vesuviana.it, which stopped working in 2002 when they were bought by 'Ente Autonomo Volturno', or EAV). I found an (all-Italian language) site for the new owner which gives up-to-date (as of 2019, but I believe it's maintained so should remain accurate) train schedules for the Circumvesuviana lines. That site is https://www.eavsrl.it/web/content/orario-ferrovia (orario is 'hours', or schedule). The part that's relevant to the Naples-Pompeii route is 'Naples-Sorrento'; both directions are listed on that page.
Brent, I'm not sure what "Circumvesuviana topic" is closed but the Sorrento website publishes the schedule for the Circ. - both directions - as it's a major destination for that line.
https://www.sorrentoinsider.com/en/naples-to-sorrento-train-schedule
Think of it like a city bus -- when you get to Napoli Centrale, walk downstairs, buy a ticket and take the next train going to Sorrento. If you just missed one, another will be along soon.
There are things that you need schedules for and others that you don't. Given the frequency that the Circum.... goes, who needs a schedule? Just show up. Worse case wait ten or fifteen minutes. Since this is Brent's first posting and very unusual for a first posting, I would be very careful of following his link.
Yes, Kathy, I should have acknowledged your Naples-Sorrento schedules, which are accurate and maintained, unlike the old circumvesuviana.it link, which has been defunct for more than a decade and which is referred to in the old Circumvesuviana topic. And for most of us tourist-people (the ones most relevant to RickSteeves.com) that's the line we want to know about. And yes, they come just about every half-hour so you don't usually have to wait long. However, your Naples-Sorrento schedule page, useful for those going from Naples to Pompeii-Scavi (and other locations on that line), does not give the other Circumvesuviana lines. Surprisingly, the Wikipedia article on circumvesuviana also only refers to the old link, though it does refer to circumvesuviana's post-2002 ownership by EAV ("Ente Autonomo Volturno"), which provided the hint I needed to find the new schedules for all circumvesuviana lines. I kept looking for those because I needed to get to the Pompei town, not Scavi, and it's on a different line, and I was also interested in the return schedule from there because I needed to time it to catch a Naples-Rome train at a specific time (and yes, I could have just walked or bussed the mile to the Scavi stop, but that doesn't make irrelevant a desire to know the Pompei line schedule, especially since it's not as frequent as the Scavi one.)
And sure, as Frank points out, I haven't posted here before, and I suppose you can simply distrust or ignore the information I provided, but it IS an accurate link, maintained by its provider, to ALL of the EAV circumvesuviana lines and their current schedules. Circumvesuviana goes more places than Sorrento, and when and where those stops are, and how long each trip takes, is useful information for some of us. I hope it's helpful for you and I believe doesn't detract at all from the very-useful Naples-Sorrento schedule that Kathy's group provides and maintains--thank you for that!
...and the other nice thing about Kathy's Sorrento group's schedule is that it's in the midst of an informative English-language site, unlike the EAV site, which is all in Italian and has no English option. However, once you find the schedules page from all their other pages, which is the link I provided, figuring out the one you want from all the routes listed is not too hard, and I believe most of us know how to read a train schedule once we find it. The UnicoCampania site (sort of a chamber-of-commerce-like site by the folks of the Campania state, home of both Pompeiis, helpfully also in English) shows on one of its maps all three lines which touch Pompeii and Pompei: the Scavi one, which also goes to Sorrento as we all by now know, the Pompei-Santuario one on the north side of the new town and is a line that goes toward Poggiomarino, and Pompei (right in the middle of town and south of the Santuario site; it's on a line that goes toward Salerno). If you're interested, and if you trust the links I'm providing (sorry, Frank), that map, which gives an excellent overview of where the ruins are in relation to the town, can be found at http://www.unicocampania.it/files/mappe/pompei.pdf. I wish I had found it earlier myself! That map is much like a black-and-white one the folks at the tourist desk near the Pompei center gave me when I arrived, but this is in color and I think informative and useful. Now I'll be quiet.
...unlike the old circumvesuviana.it link, which has been defunct for
more than a decade and which is referred to in the old Circumvesuviana
topic.
Sorry, Brent, but I've still no idea what old topic or link you're talking about but no matter.
Yes, the Circ has more than one line and yes, the www.eavsrl.it/ website publishes the individual schedules. I only linked the Napoli> Sorrento info in the other website I did as that line was specifically mentioned in your first post.
Trenitalia trains also service Pompei: that third station "right in the middle of town".