Abstract: The present study is a meta-analysis on clinical trials evaluating the efficacy of oximes on organophosphorus (OP) intoxication treatment. PubMed, Scopus, Google Scholar and clinicaltrials.gov were searched for studies investigating the effects of oximes in the treatment of OP poisoning. Mortality, intermediate syndrome, Intensive Care Unit (ICU) admission rate, hospital stay duration and intubation rate were the key outcomes of interest. Data were searched in the time period of 1966 through April 2014. Thirteen studies (eleven clinical trials and two historical cohorts) that met our criteria were included in the analysis. Pooling of data showed that Relative Risk (RR) of need for intubation in OP poisoning for ten included trials comparing oximes with placebo was 1.18 with 95% CI = 0.76 to 1.84 (p = 0.27). RR of the single observational study was 1.57 (95% CI = 0.79 to 3.2, p>0.05). The summary of RR for mortality rate in 11 studies was 1.4 (95% CI = 0.77 to 2.54, p = 0.41) and for two observational studies was 1.19 (95% CI = 0.5 to 2.85, p>0.05). The RR for ICU admission rate in OP poisoning for three trials comparing oximes to placebo was 2.12 with 95% CI = 0.89 to 5.03 (p = 0.09). For the single observational study, RR was 0.81 (95% CI = 0.49 to 1.25, p>0.05). For intermediate syndrome while the RR of only trial comparing oximes with placebo was 1.89 (95% CI = 1.27 to 2.91, p<0.05), for the single observational study, it was 1.43 (95% CI = 0.7 to 2.96, p>0.05). For hospital stay duration (difference), the RR of four studies was 0.75 with 95% CI = -0.51 to 1.99. According to these data, oximes beneficence in OP poisoning is unclear and there is a potential increase in the incidence of intermediate syndrome.