At the time, rediscovery of exchangeable aluminum in the mid 1950's seemed to be a simplifying and unifying concept. That has not turned out to be the case. Rather, as more studies have been made we have come to know less what to expect in any given soil. Examples are polymer formation, interlaying of clay minerals with hydroxylated aluminum species and the reactions of aluminum with organic substances in soil. Viewed with the hindsight of 30 years, the exchangeable aluminum concept is still of great practical importance, but includes only one of the many fates of aluminum in soils. This paper discusses the findings made on aluminum since the 1950's and makes an attempt to rank their importance according to the opinion of the author.