To identify the pattern and determinants of psychiatric illness and the predictors of long stay among long-stay patients at the Mental Health Hospital, Taif, Saudi Arabia, we examinede a total of 430 records of patients who had been admitted during the period January 1999–January 2009 and had stayed for > 9 months. More than half these patients had a history of drug addiction (60.7%). The majority were diagnosed with schizophrenia (88.8%) and mental retardation was reported in 17.7%. Personality disorders and epilepsy were diagnosed in 3.7% and 1.9% of the participants respectively. The mean duration of hospital stay was 6.16 (standard deviation 2.32; range 1–10) years. Multivariate logistic regression analysis showed that patients diagnosed with schizophrenia accompanied by mental retardation, those with lower education levels, and those with a history of co-morbid chronic diseases stayed for more than 2 years.