In the above study the growth and colonization of blow flies of species Chrysomya rufifacies (Diptera: Calliphoridae) were studied under different environmental conditions at Noida, Uttar Pradesh, India. On the basis of result it was clearly seen that a changes in temperature and humidity bring about a significant changes in growth pattern of the larval stages. In the condition with the higher temperature larva developed quickly and matured into pupa when compared to the sample grown in cooler temperature. It was also noted that fly larva grew and mature faster when they were placed under humid conditions. This study investigated the effects of drugs ethanol and cannabis on growth rates of the blowfly. Where the control sample took an average of 4 days to grow from 1st instar to pupae stages, the samples grown in the presence of ethanol and cannabis showed a much faster growth rates. Therefore it can be concluded that both the studies that were put forward before the start of this study have been proven and that the differences in environmental conditions and presence of drugs affect the growth and colonization of blow flies. This study demonstrates again the necessity of considering the possible effects of drugs in tissues on insect growth rates when estimating the postmortem interval (PMI) using entomological techniques.