The myometer has been recommended as a quantitative method of measuring muscle strength in clinical practice. The reliability of the myometer was tested in a clinical environment by physiotherapists and a form incorporating the testing positions was designed. An intensive training programme for examiners was instigated and piloted on normal subjects. The study tested the reliability of paired examiners in recording the muscle strength of 20 Guillain-Barre syndrome patients at different stages in their recovery. Ten patients were tested in the first experiment. The error rate between observers was large and unacceptable. Procedures for improving reliability were implemented. Testing was repeated on 10 more patients but no improvement in reliability was observed. The implications for clinical practice are discussed.