This paper presents a general hydrothermal route to multi-morphology manganese oxide (RMnO3, R=Ca, Sr, Ba) nano- and microcrystals and reports the magnetic properties of their nanowires as well. Adjustment of the synthesis conditions, particularly the change of the concentrations of n-hexadecyltrimethylammonium bromide and NaOH, led to the formation of nano- and microcrystals with wire-, belt-, pyramid-, flower-, and arrow-like morphologies. Considering the shape-dependent magnetic properties of nanocrystals, nanowires were selected as representative samples for magnetic measurements. At low temperature, the nanowires exhibited interesting competing ferromagnetic antiferromagnetic interactions, and the magnetization values increase significantly with increasing the radius of positive ions from Ca2+ to Ba2+. (C) 2013 Elsevier By. All rights reserved.