Background The enlarged prostate leads to obstruction and lower urinary tract symptoms (LUTS), which comprise frequency, urgency, weak stream, straining and nocturia. This study was conducted in a large series of patients to evaluate the relationship between LUTS as stipulated in the International Prostate Symptom Score (IPSS) and the objective parameters related to benign prostatic hyperplasia (BPH).Methods We enrolled 1295 BPH patients from seven centers. The patients were either at first diagnosis of BPH or had discontinued medical treatment for at least 3 months. Those with several other diseases that may be potential risk factors affecting urinary symptoms were excluded from the study. Age, IPSS, prostate volume, peak flow rate, urine volume and post-voiding residual urine volume were measured. The relationship between IPSS and objective parameters were quantified by means of Spearman correlation coefficients. The differences in these parameters between the groups with mild, moderate or severe symptoms were also evaluated.Results Statistically significant correlations were found between IPSS and objective parameters by means of Spearman correlation coefficients. When the patients were divided into three groups with different severities of symptoms,there were significant differences in peak flow rate, urine volume, prostate volume, residue urine volume and quality of life, whereas average age and prostate-specific antigen levels were similar. However, there was evident overlap of these parameters between the groups. The same results were found when the irritative or obstructive subscore of IPSS was considered.Conclusions The correlation between objective parameters of BPH and LUTS is significant. However, it is hard to predict the severity of symptoms by these parameters.