We use the computer program Gaussian 03 to predict the IR spectra of ground state CH₃AsH₂ and CH₃SbH₂. The calculations are performed at HF level of theory. The 6-311G** basis set is used for methylarsine and the CEP-121G basis set is used for methylstibine. Normal mode assignments of the IR frequencies of methylarsine and methylstibine and their deuterated isotopomers are determined based on calculated potential energy distributions. The PED for each frequency is found using Kim's Correspondence Rules of unified group theory and the program MOLVIB. The predominant motion of each PED is used to name the corresponding vibrational frequency. We compare our results with literature values. Our IR frequency assignments show generally good agreement with experiment