Voting started early Friday morning in many polling stations in the Baringo South by-election with some centres reporting faulty voter identification devices.
The turnout has been low but is expected to increase as the day progresses.
Election officials at Marigat Boys High School and Kimorok polling stations were scrambling to get replacements after the Kenya Integrated Management Systems failed.
However, voting continued in other centers without hitches.
The by-election was occasioned by the death of Ms Grace Kipchoim in April.
Candidates battling for the seat are: Charles Kamuren (Jubilee), Cynthia Kipchilat (Maendeleo Chap Chap), Paul Kimaru Motoloi (Chama Cha Mashinani) and Sylvester Sergon (Republican Labour Party).
Independent Electoral and Boundaries Commission Chairman Wafula Chebukati is overseeing the voting in the constituency.
I's the first by-election occasioned by the death of an incumbent.