The nitrosation of piperidine, 2-methylpiperidine, 4-methylpiperidine, 2,6-dimethylpiperidine, and 2-ethylpiperidine in acid medium was studied. Kinetic monitoring of the reactions was accomplished by spectrophotometric analysis of the nitrosamine formed at λ = 249 nm. In each case, the value of the rate constant of the determining step R2NH + N2O3 → R2NNO + HNO2 was calculated, observing the following sequence of reactivities: piperidine ≈ 4-methylpiperidine > 2-methylpiperidine ≈ 2-ethylpiperidine > 2,6-dimethylpiperidine. In the case of 2,6-dimethylpiperidine, no nitrosation was observed. The results are interpreted in terms of the steric hindrance of the alkyl groups to attack of the secondary amine group by dinitrogen trioxide. The results open the possibility of blocking the undesirable mechanisms of formation of N-nitroso compounds. Keywords: Nitrosation; steric hindrance; piperidine and related compounds