Abstract: The effect of concentration change on the rate of killing of some selected microorganisms by ethanolic extracts from two varieties of Acalypha wilkesiana was carried out using the plate count technique. The haemolytic activities by the agar diffusion method was investigated.The killing rate was found to increase as concentration increases. This was shown by reduction in the amount of survivors in cfu mL ¹ as the exposure time progresses. The rate of killing of the microbial population by the extract was also found to be concentration dependent as increase in concentration lead to reduction in microbial loads. The relationship was established to be exponential one as revealed by the concentration queficent The two varieties of the Acalypha wilkesiana also differ in the ability to kill the different bacteria species and fungus (Candida albicans) with the macrophylla showing higher degree of killing than the Hoffmanin. Generally, the rate of killing was found to vary among the different bacteria species with gram negative ones like Escherichia coli, Klebsiella and Pseudomonas being killed at a lower rate than the gram positive organism like Bacillus and Staphylococcus. Candida albicans being a fungus was killed at extremely lower rate than the bacteria. The haemolytic activity was found to be higher in Macrophylla than Hoffmanin and the values increase as the concentration increases.