Pore size distributions in an Australian coral from Goniopora sp have been measured by mercury intrusion, nuclear magnetic resonance (NMR) and scanning electron microscopy (SEM). A significant result is that NMR predicts nanopores which could be seen visibly. The methods give similar results as mercury intrusion for large pores around 100 mum but differ for smaller pores. Differences between NMR and mercury intrusion are equated using a non linear sigmoidal regression model. The NMR method was also compared with mercury intrusion methods to measure pore sizes on hydroxyapatite conversion products which have promise as bio-implants. Differences between samples due to errors in the methodology are discussed. Together all three methods are shown to complement each other. (C) 2004 Kluwer Academic Publishers.