 Good afternoon everyone. I am Dr. Ashish Sharma, second year post graduate resident in Government Medical College, Jammu. Thank you for giving me this opportunity to present the paper and the topic for my paper presentation is city study of third and fourth ventricle size in normal North Indian subjects. Introduction. The ventricular system is a complex network of interconnected fluid filled cavities within the brain. It plays a crucial role in supporting and protecting the brain, as well as facilitating the circulation of cerebrospinal fluid. The system is embryologically derived from the neural canal, which forms early in the development of the neural tube, a precursor to the brain and spinal cord. The ventricular system consists of four main cavities, lateral ventricles. These are largest cavities and are located symmetrically in the cerebral hemispheres. Each hemisphere houses one lateral ventricle. They communicate with each other and with the third ventricle through openings called the foramina of monro. Third ventricle. Positioned in the bit line of the brain, this ventricle lies beneath the corpus callosum and above the hypothalamus. It connects with the lateral ventricles through the foramina of monro and communicates with the fourth ventricle via the cerebral aqueduct. Fourth ventricle. Located in the brainstem, the fourth ventricle is a diamond shaped cavity. It communicates with the third ventricle through the cerebral aqueduct and opens into the sub-reconant space, sonowning the brain and spinal cord, allowing CSF to circulate. The ventricular system is responsible for producing and distributing CSF throughout the brain and spinal cord. CSF provides buoyancy to the brain, questioning it from impact and helps to regulate the brain's chemical environment. Additionally, the ventricular system plays an important role in removing waste products and delivering nutrients to the brain. The advancement of the medical imaging techniques, such as computer tomography and magnetic raps resonance imaging, has greatly enhanced our understanding to the ventricular system's anatomy and function, allowing for non-invasive visualization and assessment. Ames and objectives. To establish a baseline reference value for the third and fourth ventricular width using CT for normal north Indian population. Materials and methods. 100 participants were analyzed ranging from 5 to 90 years old, among them 62 over males and 38 for females. All the subjects were divided into subgroups, based on age and sex. All had normal CT brain scans. CT brain scans, axial sections were obtained at 2 mm slice thickness, from skull base to the vertex. Then the DICOM images were analyzed on viewing console. Measurements were taken with in-bit linear calipers, which are calibrated to 0.1 mm. The widest diameter of third and fourth ventricles on axial images using linear approach was measured. Siemens somatom dual-slice CT machine was used. The total participants were 100 out of which 62 over males and 38 per females. This is the axial CT scan showing third ventricle measurement. The widest diameter of the third ventricle is measured by using linear approach. Same with the fourth ventricle, the widest diameter was measured using the linear approach. All measurements were expressed as mean and standard deviation. Student T test was used to estimate the difference in ventricular size based on sex. One way analysis of variance was used to check for differences in ventricular dimensions across age groups. Results. In this research, it was observed that the average size of the third and fourth ventricles is larger in males than in females. However, it's important to note that the difference in size does not have statistical significance. The highest value of third ventricles in both males and females was highest in 60 years. So, this is the table which shows the highest ventricle, the highest value of the third ventricle in both females and males was highest in greater than 60 years of age group. And the average value of third and fourth ventricle in males was greater than females, the average value of third and fourth ventricles in females. Discussion. In this study, we observed that the mean size of third and fourth ventricles tends to be larger in males as compared to females. Inclusion. Baseline reference values for the width of the third and fourth ventricles were acquired from subjects representing the healthy prepuse populace of North India. These findings elucidated a consistent augmentation in the dimensions of the third ventricle as individuals progressed through varying age strata. The apex of ventricular dimensions within the third ventricle was discerned within the eldest age bracket encompassing individuals exceeding 60 years of age regardless of gender. And these are my references. Thank you.