We studied the correlation between the neck muscle strength and the degree of pain in 31 women with chronic neck pain and 25 healthy women. The neck isometric flexor and extensor muscle strength were measured using FARO Axis muscle tester and Pain Disability Index(PDI) was scored in the chronic neck pain patients at the beginning and at the end of the 4-week rehabilitation training including neck isometric exercise(NIE), electrical theraphy, heat therapy and traction. At the beginning of training, there was significant decrement of the neck muscle strength in the patient group compared with the control group and the PDI was correlated with the neck muscle strength significantly. After the 4-week training, significant increment of the neck muscle strength and decrement of the PDI were noticed. there were significant correlations between the increment of neck muscle strength and the reduction of PDI. This study was concluded that neck muscle strength measurement is useful in diagnosis and follow up of the chronic neck pain patients and neck isometric exercise is effective in strengthening of neck muscle and pain reduction.