The cationic interference in the analysis of mercury at trace level by cold vapour atomic absorption spectroscopy (CVAAS) has been investigated. Different cations (Na+, K+, Fe2+, Zn2+, Cr3+, Co2+, Ni2+ and Cu2+) of varying concentrations are examined as possible interferents in the analysis of mercury. Na+, Fe2+, Zn2+ and K+ did not show any affect due to their presence in the detection of mercury while Co2+, Ni2+, Cu2+ and Cr3+ had a marked influence on mercury recovery and can be suggested as possible interfering agents for this method of Hg analysis.