Spontaneous growth of 141 untreated girls with Turner syndrome was analysed. Of the patients 25% were born prematurely; their weight and height were normal when compared to prematurely born healthy infants. However, birth weight and height was significantly retarded in Turner patients born at term. A curve for height and growth velocity for the age range 0-16 years was constructed with a sensitive statistical method. By use of a mathematical model equations were created for calculating z-scores and the related percentiles for the height of individual patients at given age. Median height of 18 untreated patients at 18 years was 143.8 cm. Analysis of growth velocity revealed a minor but significant growth spurt at the age of 12.5 years. This growth spurt was also detectable in patients without signs of spontaneous puberty and occurred later in patients with 45,X0 karyotype. Bone age progression was linear up to the age of 7.5 years and decelerated thereafter.