Here are details of all the county signings and departures from the 2018 season.
Counties are allowed to field two overseas players in Twenty20 games, with up to four registered for that competition, although only two can be registered at any one time, and registrations must be for a minimum of 10 days.
Only one overseas player is permitted in the County Championship and One-Day Cup competitions.
Guide to abbreviations
Also shows, where relevant, players' previous counties
KPK: Kolpak contract
YTH: From youth teams
EUP: European Union passport
UKP: Born overseas, but has UK passport
Kolpak contracts are signed by foreign players, using a European Court ruling to avoid counting against the quota of one overseas player per club.
Players who moved counties or retired during the 2017 season are included on the 2017 list. Have we missed anyone? Please let us know.
Other news: Batsman Jack Burnham was banned for the 2018 season after receiving a one-year ban for recreational drug use. Latham captained in the One-Day Cup and T20 Blast following Jennings' and Coughlin's departures.
Overseas player: Shaun Marsh (Australia, until 8 July); Usman Khawaja (Australia, as cover for Marsh from 9-28 June and then for Twenty20 until 4 August); Joe Burns (Australia, for Twenty20, 20 July-2 August); Stephen Cook (South Africa, from 1 September)
Overseas player: Hashim Amla (South Africa, first two months of season); Dale Steyn (South Africa, 6-28 June & 8 August-11 September); Colin Munro (New Zealand, for Twenty20 until 3 August); Mujeeb Ur Rahman (Afghanistan, for Twenty20 until 15 August)
Other news: Keeper-batsman Sam Billings was appointed as captain after Northeast was replaced before his departure, with Paul Downton becoming director of cricket. Meanwhile, Allan Donald took up his role as assistant coach after finally receiving a work permit.
Other news: Former captain David Sales became full-time batting coach after a part-time spell in the role. Spinner Graeme White retired from first-class cricket on 19 June to concentrate on limited-overs formats.
Overseas player: Dean Elgar (South Africa, first two months of season and from 29 August); Theunis de Bruyn (South Africa, 20-28 June); Aaron Finch (Australia, primarily for Twenty20 from 12 July); Nic Maddinson (Australia, for Twenty20 from 12 July)
Other news: Coach Mark Davis left the club in November 2017 and was replaced by Jason Gillespie. Academy director Carl Hopkinson left to become the ECB's lead fielding coach, and was replaced by ex-England assistant coach Richard Halsall. Meanwhile, Sussex assistant coach Jon Lewis departed to become England Under-19s coach. Ben Brown was named club captain and led in the Championship and One-Day Cup, with Luke Wright as T20 captain.
Other news: Patel was appointed captain for the Championship and One-Day Cup, with Grant Elliott taking on the role for the Bears in the T20 Blast. Bowling coach Alan Richardson left Edgbaston by mutual consent and was replaced by Graeme Welch, who returned to the club from Leicestershire. Head of strength and conditioning Chris Armstrong also departed.
Overseas player: Travis Head (Australia, until 29 May, then from 13-15 July); Callum Ferguson (Australia, for One-Day Cup from 29 May, then first three Twenty 20 games and from 3-17 August); Martin Guptill (New Zealand, for Twenty20, 20 June - 29 July); Wayne Parnell (South Africa, 19 July-15 September, then as a Kolpak signing from 17 September)