1999–2000 National League 1
The 1999–2000 National League 1, sponsored by Jewson, was the thirteenth full season of rugby union within the third tier of the English league system.
Structure
The league consisted of fourteen teams, playing each other on a home and away basis to make a total of twenty-six matches for each team. There were two promotion places with the top two teams promoted to the newly named 2000–01 National Division One. Two teams were relegated to either National League 2 North or South, depending on geographical location.Participating clubs
Ten of the clubs participating in last seasons competition. To make up the numbers two of the teams were promoted from National 2 North, and two from National 2 South were also promoted.| Team | Ground | Capacity | City/Area | Last season |
| Birmingham & Solihull | Sharmans Cross | 2,500 | Solihull, West Midlands | 11th |
| Blackheath | Rectory Field | 6,000 | Greenwich, London | Relegated from Premiership 2 |
| Bracknell | Lily Hill Park | 1,000 | Bracknell, Berkshire | Promoted from National 2 South |
| Camberley | Watchetts | Camberley, Surrey | 9th | |
| Fylde | Woodlands | 9,000 | Lytham St Annes, Lancashire | Relegated from Premiership 2 |
| Harrogate | County Ground | Harrogate, North Yorkshire | 12th | |
| Lydney | Regentsholm | 1,500 | Lydney, Gloucestershire | 8th |
| Newbury | Monks Lane | 8,000 | Newbury, Berkshire | 6th |
| Nottingham | Ireland Avenue | 4,950 | Nottingham, Nottinghamshire | 4th |
| Otley | Cross Green | 5,000 | Otley, West Yorkshire | 5th |
| Preston Grasshoppers | Lightfoot Green | 5,000 | Preston, Lancashire | Promoted from National 2 North |
| Reading | Holme Park | Sonning, Berkshire | 10th | |
| Rosslyn Park | The Rock | 2,000 | Roehampton, London | 3rd |
| Wharfedale | The Avenue | 2,000 | Threshfield, North Yorkshire | 7th |