age between 18-55 years

confirmed multiple sclerosis diagnosis according to mcdonald criteria

stable neurological functioning for at least one month prior to study entry

expanded disability scale score (edss) less than <_4.0

must have had one clinical attack in past two years and at least one new silent t2 or gadolinium-enhancing lesion on mri within the past one year.

willing to participate for the entire 52-week period

pregnant or nursing.

connective tissue disease (sle, sjogren's disease)

endocrine disease (hyperthyroidism, hyperparathyroidism)

any medical condition predisposing to hypercalcaemia, nephrolithiasis or renal insufficiency