Does association mean causality? George Somers, Monash University 26 April 2013 Thank you for this paper. Unfortunatley, only the abstract is available at this stage, the full paper, when it becomes available, might explain my question. From the abstract, it seems that when you conclude that increasing the length of rural rotations to three years 'significantly increases the likelihood of rural career intentions of non-rural students' you are implying causality. If you merely found that an increased association was observed, have you shown that it was the rural experience that caused the increase in intention? Other readers of your abstract might also infer that causality was shown. Perhaps this is only my interpretation of your sentence, however such ambiguity cannot be ignored. In a recent study I found that the intention of those who chose to undertake longer rural rotations was already higher at entry to the rural program. I found that the decrease in rural intention observed in the whole cohort over the three years was not influenced by length of rural rotaton. I concluded that it was this stronger interest in a rural career that motivated students to undertake longer rural rotations not the other way around. (Somers GT, Spencer RJ. Nature or nurture: The effect of undergraduate rural clinical rotations on pre-existent rural career choice likelihood as measured by the SOMERS Index. Aust J Rural Health. 2012;20:80-7. Epub 7 January 2012.) I raise this issue because most papers written on this subject have been produced by and refereed by employees of Schools of Rural Health with a vested interest, raising the risk of publication bias. Competing interests A competing interest exists when your professional judgment about a paper could possibly be influenced by considerations other than the paper's validity or importance. Detail possible competing interests here... I have no competing interest.