Three compounds, SrTa2O6, Sr4Ta2O9, and Sr5Ta4O15, were synthesized by a polymerizable complex method. Their photocatalytic activities for water splitting into H-2 and O-2 were tested and compared against previously published results for Sr2Ta2O7. It was found that the efficiency of the catalysts decreases in the following order: Sr2Ta2O7 > Sr5Ta4O15 > SrTa2O6 > Sr4Ta2O9. The relationship between photocatalytic activities and crystal structures is discussed. © 2005 Elsevier Inc. All rights reserved.