Prevalence estimates of alcohol abuse or dependence in general hospitals are often limited to single wards, small data collecting periods or insufficient diagnostic procedures. Therefore, the present study aimed to ascertain alcohol abuse or dependence in one general hospital, to compare prevalence data for all the 11 wards and 6 intake months, to establish if screening is sufficient or if a two-step diagnostic procedure is needed, and to determine whether information for an alcohol diagnosis on suspicion is available. A sample of 1309 medical or surgical in-patients were screened by questionnaires or medication for withdrawal, and, if screening-positive, were interviewed with the alcohol section of a standardized psychiatric interview. In screening-negative patients, a diagnosis on suspicion was given if medication to treat withdrawal had been used, or if there was evidence of single criteria of alcohol dependence, somatic disorders from alcohol drinking, raised laboratory parameters on grounds of alcohol drinking or of self-reported high alcohol consumption. Of the medical and surgical in-patients, 20.7 and 16.0% respectively were alcohol abusers or dependants, with a range of prevalence rates of alcohol abuse or dependence among wards of 11.1–32.9% and among intake months between 11.3 and 28.7%. Of the medical department in-patients, 1.9%, and of the surgical in-patients, 2.1%, were screened as false-positive cases. In addition, 5.5% of the medical and 12.0% of the surgical patients were given a diagnosis on suspicion. It is concluded that all general wards and different intake months should be taken into account when estimating prevalence of alcohol abuse or dependence in a general hospital.