We retrospectively analysed patients with histologically proven Rathke's cleft cyst (RCC) in relation to the clinical manifestations and MRI findings, in particular, of cyst size and intensity in order to obtain an insight into their growing mechanisms, clinical presentations and their management. Eleven patients with RCC were divided into two groups based on T1 weighted images(WI). The A group consisted of 4 patients with cyst of low intensity in T1 WI. The age averaged 64.5 years. Their initial complaints were visual field defects(VFD). Their complaints were rather insidious. The maximum cyst size averaged 27.8+/-2.4 mm. The B group consisted of 7 patients with cyst of iso- or high-intensity in T1 WI. Two patients in the B group showed mixture of low and high and iso- and high-intensity, suggesting the presence of bleeding at the onset of symptoms or growing mechanism of the cysts. In the B group the age averaged 39.9 years, being lower than that in the A group. (P=0.0140 with Mann-Whitney's U test) The 5 patients out of 7 showed headache of insidious type or acute onset and the 3 showed a fluctuation of the VFD. The average size was 21.7+/-3.5 mm and smaller than that of the A group. (P=0.0298 with Mann-Whitney's U test) Our study has shown that the cyst with iso-to high intensity on T1 WI may cause clinical symptoms with a smaller size than cysts of the low intensity. In the former cyst pattern the onset and growing mechanism may be related to bleeding. The patients with this pattern are more likely to have acute and/or fluctuation of clinical presentations. Knowing these various clinical manifestations based on MRI pattern will be of help in following and managing patients with RCC.