The effects of phosphate, aluminium, sodium and potassium on the atomic fluorescence of calcium at 422.7 nm and the ionic fluorescence at I:393.4-396.8 nm have been studied. When the operating conditions are optimised for maximum fluorescence signal from a solution containing no interferents, interference effects are observed which may be interpreted in terms of stable compound formation, ionisation suppression and fluorescence quenching. These effects may be removed by optimising the operating parameters for minimum interference.