1999–00 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. Due to league restructuring for the 2000–01 season, the league would be renamed to National Division Two for the following season, with the old Allied Dunbar Premiership 2 being renamed as National Division One.
Otley would finish the season as league champions, and along with runners up Birmingham & Solihull would be promoted to the new look National Division One. Relegated sides included Reading and Blackheath who both dropped to National League 3 South.
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 3 South or National League 3 South, depending on geographical location.Participating clubs
| Team | Ground | Capacity | City/Area | Previous season |
| Birmingham & Solihull | Sharmans Cross | 4,000 | Solihull, West Midlands | 11th |
| Blackheath | Rectory Field | 3,500 | Greenwich, London | Relegated from Premiership 2 |
| Bracknell | Lily Hill Park | 1,000 | Bracknell, Berkshire | Promoted from National 2 South |
| Camberley | Watchetts | 2,000 | Camberley, Surrey | 9th |
| Fylde | Woodlands | 7,500 | Lytham St Annes, Lancashire | Relegated from Premiership 2 |
| Harrogate | Claro Road | 4,500 | Harrogate, North Yorkshire | 12th |
| Lydney | Regentsholm | 3,000 | Lydney, Gloucestershire | 8th |
| Newbury | Monks Lane | 8,000 | Newbury, Berkshire | 6th |
| Nottingham | Ireland Avenue | 4,990 | Nottingham, Nottinghamshire | 4th |
| Otley | Cross Green | 7,000 | Otley, West Yorkshire | 5th |
| Preston Grasshoppers | Lightfoot Green | 2,250 | Preston, Lancashire | Promoted from National 2 North |
| Reading | Holme Park | Sonning, Berkshire | 10th | |
| Rosslyn Park | The Rock | 4,630 | Roehampton, London | 3rd |
| Wharfedale | The Avenue | 2,000 | Threshfield, North Yorkshire | 7th |